False myths about achromats - again and again.
ValeryD
he read somewhere in Yahoo news groups.
He re-sent me a very interesting, to some degree typical, post.
Here is a part of it:
>>I will tell you that there is a Stellarvue 1010 owner who also owns
a Vixen 102ED and TV Genesis who has stated that the 1010 performs
nearly as well as the 102ED in terms of color aberration and that it
can be pushed to nearly the same magnification before image breakdown
and that's for a 80mm scope. I can also tell you that reports of the
102D from recent owners state that it achieves even better color
correction than the 1010 and can easily be pushed to over 240x
atmospheric conditions allowing. All achromats are not the same. I
think anyone with an objective viewpoint would accept this. In any
case I will let you all know how the 102D performs in a couple
months. If you want to get a taste of it's performance right
now,
check out the Stellavue Yahoo group or Stellarvue's web site. Well
worth it for anyone considering a 80mm to 102mm refractor.
Regards.
Tom.
>>
What I can say?
1. Vixen ED refractor glass combination allow to have 5x smaller
secondary
spectrum than the in a _best possible achromat_ of the same D and F/D
.
2. Magnification pushing depends not only from color correction. It
mainly
depends from spherical aberration correction, optics smoothness and
seeing conditions. So, the fact, that magnification in simple
achromats
can be pushed to 240x is not any kind of unique fact. In _any_
achromat
with well corrected spherical aberration and smooth optics and under
good
seeing conditions magnification can be pushed even higher - to about
400x
(when observing double stars, for example).
3. False color perception greatly depends of used magnification and
atmosphere transparency. As higher magnification, as lower surface
brightness of a false color halo. At 2000x in 4" achromat one will not
see any false colors on moon or even Jupiter.
At foggy conditions violet-blue false colors will be also greatly
reduced.
4. Some peoples, especially older persons, has greatly reduced eye
sensitivity to a violet part of spectrum.
Some peoples (mans 5x more often than womans) are colorblind in some
degree.
Both these factors can influence a color error estimation too.
5. Finally, some peoples simply don't like to see a false colors and
make
statements like above.
The difference between Vixen achromat and ED APO is well seen in their
prices. This price difference correctly reflects a differnce in color
correction for both these scopes.
It is simply impossible to create an achromatic objective of the same
D
and F/D which will stay even close to true (not fake) ED APO.
Vixen's optical designers have the same (or better) access to
different
optical glasses as designer of these miracle achromats. They also not
a bit less experience in optical desing science than 102D designer.
However they are unable to create such achromat, that will approach
a color correction performance achieved in ED APO.
False myths have a unique property to survive in some sort of minds.
This can't be argued at all. Above letter is a very good sample of
this.
Valery Deryuzhin.
ARIES.
Chris1011
and F/D which will stay even close to true (not fake) ED APO.>>
What you say is true, but people will always hope for miracles - especially
cheap ones. And there is always someone there ready to sell them one.
Roland Christen
Larry Brown
apochromatic to anyone who can prove they are colorblind."
Clear skies anyway.
Larry Brown
Dan Chaffee
> 3. False color perception greatly depends of used magnification and
> atmosphere transparency. As higher magnification, as lower surface
> brightness of a false color halo. At 2000x in 4" achromat one will not
> see any false colors on moon or even Jupiter.
But, I hope no one comes away with the idea that at such high
power, or at even >20x/cm aperture, a traditional crown-flint
doublet will show bright objects at their _true_ color. I.e, a
friend's 20cm f/15 Fraunhofer starts showing Saturn as noticeably
more yellow-orange than a perfectly apochromatic system at 250-300x.
D Chaffee
Ron B[ee]
For my own optically inept education, is it true that there is range of
achromat
glass (crown/flint) and there is a range of ED glass and there is a range of
flourite lenses as well. By "range", I mean the degree that the glass can
correct
chromatic aberration (leaving everything else such as spherical aberrations
as
equal). Thus, for instance, a low-end ED glass would not yield as good a
correct as high-end ED glass. If so, is it also true that there's a large
price
difference with the range of these types of glasses/flourite crystals?
Thanks,
Ron B[ee]
-----------
"Chris1011" <chri...@aol.com> wrote in message
news:20011003103149...@mb-md.aol.com...
Ron B[ee]
my old 4" f/9.8 C102-HD achromat than my 4" TV-102 APO.
Although there's no chromatic aberrations (i.e. purple halo
that I can see) with Saturn, there seem to be a veil of slight "fog"
(for a lack of better description) around the ring and the
planet through the C102-HD; whereas I don't see this effect
through my TV-102.
Ron B[ee]
-----------
"Dan Chaffee" <dcha...@blitz-it.net> wrote in message
news:67806d2a.01100...@posting.google.com...
Dave
Val:
You and Roland just simply amaze me. It's almost unbelievable, but
then you have a vested business interest and Roland must have
forgotten the enjoyment of stargazing.
I have a Stellarvue. It is an achromat. It is a very well made
achromat with excellent optics, minimal if any coma and astigmatism.
It is an achromat. It has always been advertised and promoted by
Stellarvue as an achromat. Unless someone has been in this hobby for
less than a month, everyone knows what an achromat is. Stellarvue has
never claimed that the 80mm f6 or the 102D or 102EDT is an APO. There
is no conspiracy here, unless there's one between yourself and Roland.
There are no false claims being made by Stellarvue, no promotion of
"miracle achromats", no false dreams of a cheap apo, no claim of
completely eliminating color, and not even one claim of being a
"semi-apo"...whatever that is (ask William Yang, maybe he knows).
You are taking a cheap shot at the posting of an observation session.
Did both of you forget that astronomy is about OBSERVING? The
individual quoted here compared her 102Vixen ED with her 80mm F6. They
are both her scopes. She reported what she observed. That is what
amateur astronomy is about...not bickering between some old men with
nothing else to do. You point out very valid reasons as to why she may
have observed what she observed (ability to detect color, eyepiece
selection and magnification, weather, etc). However, this was her
observation. Have you compared an 80mm F6 Stellarvue to a Vixen ED?
No. How can you place yourself in the position of telling us what this
observer saw. Neither of you can. This whole posting is ludicrous and
to take it and transfer it to false claims being made by a
manufacturer are just absurd.
David
Chris1011
glass (crown/flint) and there is a range of ED glass and there is a range of
flourite lenses as well. By "range", I mean the degree that the glass can
correct
chromatic aberration (leaving everything else such as spherical aberrations
as>>
The answer is NO and YES.
NO, there is no range of achromat color correction. Achromats are made from
ordinary glasses that have no special dispersion characteristics. An achromat
is made with a crown positive element and a flint negative element. These
glasses are made with various oxides, which give them their strength and
durability. Normal dispersion glasses will correct the colors from C to F to 1
part in 2000, or the focal length will vary by .05% from red to green to blue,
and approximately .25% for violet. The amount of color halo you see around a
star with any aperture will be inversely proportional to the focal ratio. Thus
an f15 scope will have half the color halo of an F7.5. A 20"F15 achromat scope
will have the same size color halo as a 4"f15 achromat, but because the 20" has
1/5 the size Airy disc, the color relative to the Airy disc max resolution will
be 5 times worse for the 20" vs. the 4" scope. What happens if you add a third
element? Nothing, the color correction is still 1 part in 2000. You can add 50
elements, and you won't gain anyhting.
YES, there is a difference between various ED and Fluorite scopes, but it is
not really the ED or Fluorite that governs the amount of correction, but the
mating element. Normally, even the worst ED design will have 4 times better
color correction than a normal achromat, but it could easily be 20 times better
simply by choosing a different mating element. The more expensive the ED, the
easier it is to mate it to a corresponding negative element to achieve perfect
color correction.
You can make an ED lens with an ED positive element, and a flint negative
element just like an achromat, but the color correction will not be very good,
perhaps a semi-apo. By choosing a Short-Flint or Crown-Flint you can get better
correction, but not perfect cancellation of secondary color - perhaps 4 to 6
times reduction depending on the combination. To get perfect cancellation over
a wide wavelength range you would mate the ED with a negative element made with
Crown glass. These are the most difficult to make, so commercial Apo makers
avoid these.
What gives the ED material the ability to correct color? It is the chemical
composition of the material which is based on fluorides instead of oxides.
Fluoride based glasses have a different dispersion characteristic caused by
absorption bands that are further away in the ultraviolet (this also allows
them to pass UV light more readily).
The drawback of fluoride based glass is that the bonds that fluoride forms
with other materials are weak (oxide compounds are very strong and super hard).
The fluoride material is hard to polish and stains more readily in some cases.
I hope this answers some questions, sorry it was so long winded.
Roland Christen
Ron B[ee]
I've learned a lot from your various thesis as well as from your
various postings both here an the ap_ug eGroup.
Thanks for taking the time.
Ron B[ee]
-----------
"Chris1011" <chri...@aol.com> wrote in message
news:20011003190802...@mb-md.aol.com...
...snip...
Chris1011
One more comment, it is possible to make a so-called "ED" lens and have normal
achromat correction of 1 part in 2000. There is one glass that some call ED -
FK5, which will produce the same correction as any normal achromat combo. It's
also exceedingly cheap.
Schott has given FK5 the designation FK (fluoro-crown), but it has no
particular color correcting properties in the normal visual wavelength range.
Yet, this does not prevent slick marketeers to call a lens made with this
material an "ED" lens, hoping that people will assume it is also an Apo. It
ain't no way an apo!!!! By the way, lots of these "ED" refractors have been
made and sold by various outfits. Tom Back and I refer to FK5 as "Fake ED"
glass.
Very confusing, yes?
Roland Christen
Randy Roy
Roland--I assume this a "cheap" shot about the Chromacorr. Shame! And
besides, they are not cheap!
Randy
chri...@aol.com (Chris1011) wrote in message news:<20011003103149...@mb-md.aol.com>...
Brian Tung
> Roland--I assume this a "cheap" shot about the Chromacorr. Shame! And
> besides, they are not cheap!
I don't think so. I think I know what Roland is talking about, and if
so, it's not the Chromacorr.
Brian Tung <br...@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
William Mc Hale
: Val:
Dave,
I think you are being a little too hard on Roland and Valery. Alot of
people when looking for a telescope read the reviews here or on the
Telescope Mailing list. If it is there first telescope; and perhaps they
have only looked through a high quality APO, they might believe the hype
given to some scopes. I have heard enough reports of the Stellarvue to
believe that the 80mm at least is an excellent scope, but they are right
to say that it can't deliver near Apo performance. Perhaps, and this is
just a guess, it might be that there are quite a few poorly made achromats
out there that do not correct for color as well as they should and in
comparison a well corrected example will seem to be nearly an APO in
performance. Just a thought.
--
Bill
***************************************************************************
Despite the cost of living, have you noticed how popular it remains?
---------------------------------------------------------------------------
Home page - http://www.gl.umbc.edu/~wmchal1
***************************************************************************
Darren Hennig
I tell you, this is getting B-O-R-I-N-G!!!
Roland and Val, do you want to REALLY impress the amateur community? Okay,
here's a challenge for ya - make an apo for US$1,000. Say a 4". Can ya do
it? eh? Okay, maybe that's pushing it - try for $1500-1700 US. OTA only, we
don't want to push our luck. Triplet is fine. How about at least 1/30 wave
RMS error too.
I get soooo tired of this assumptive bushwacking you boys are doing.
Actually, in Roland's defense, he at least posts technical information of
value - mostly accurate. Val - what are you doing, sir?! I do not know what
the agenda is here fellows, but in defense of the Stellarvue line, these
aren't magical scopes, Vic Maris does not sell some sort of pharmacological
accessory to enjoy the views with, nor does he put his customers on some
sort of payroll. The scopes he sells work, and work well. They fill a niche
that obviously was there. They ARE achromats, albeit well corrected. They
ARE affordable, and they HAVE great optics - period.
Stellarvue customers are loyal, both because of the design philosophy and
ethical practices Vic adheres to, and because they appreciate real VALUE.
Roland, there's no question in my mind that your scopes are top-notch all
the way. They have set a very high standard that many use as a benchmark.
Bravo to you for this! But I find it odd that you guys need to flood the
group with optical technojargon to the extent that the original issues are
lost somewhat in the discussion. It becomes a "why an acromat can't have
reduced color beyond a certain point" thread again and again! Think about
the former challenge I submitted - I think that if you could do this, you
would not even bother worrying about anything.
So, let's start enjoying observing again - afterall, that's what this hobby
is about - if you want to talk jargon, start an sci.telescope.optics group
or something - GEEZ!
Dismayed and disappointed...
rande...@home.com
Synta-Chromacor combination.
-Rich
Peter Besenbruch
<dhen...@teluaplanet.net> wrote:
>but in defense of the Stellarvue line,
Who attacked Stellarvue? I haven't seen their name mentioned once
by either Valery or Roland.
__________________________________________________________
http://www.hawastsoc.org/ (Hawaiian Astronomical Society)
http://www.hawastsoc.org/deepsky/ (Deepsky Atlas)
ValeryD
What completely amazed me is that a well known name of one type of your
famous objectives(scopes) EDT was used by mgf of these cheap achromats!
Of course, this was done in marketing pursuit. But how modesty!
I will not wonder if THIS model has an internal stop for color correction
"improvement".
One carefully work with caprise glasses, another one is so clever, that
he discovered a new method of color "correction" in junction with tales,
that HIS achromats are nearly as good as APOs are. SHAME!
Really, it is almost fun to see such claims - " THIS achro is almost same
good as APO", "THIS optics is1/63 wave" etc etc, but only if one forgot,
that peoples pay their hardly earned money for these myths.
They always have alternatives, but such myths "gravitate" them constantly.
Valery Deryuzhin.
Anders Hansson
Don't expect too much from this thread.
This is not about optics at all, it is about a failed business
relationship and a desire to get even.
Anders H.
--
Note: There is a small intentional error in my domain name, it should
end with the following: ericsson.se. All opinions are strictly my own.
Dave
Bill:
If the intent of the posting was to explain why this observer
experienced what she saw, then I would have no problem. However, Val
took this observation, tied it to Stellarvue, and insinuated that the
company is claiming apo performance at achromat costs. This is simply
This is simply not a true statement. They are not advertised as such
and Val and Roland know that. Val has an issue with Stellarvue in that
he wanted Stellarvue to promote his chromacor. Val came on to the
stellarvue groups site and announced that he had run some simulations
on a computer and that the chromacor would eliminate false color on
the 102D. The incredible thing about it was that he had not tested it
with the acutal scope. His "simulation" is worthless because he does
not know the optical characteristics of the 102D lens (he didn't even
know that it was a f6.9, doesn't know what glass is used or which
wavelengths need "correction"), etc, etc. From an optical engineer's
perspective, this was completely unprofessional. He'd be fired if he
worked for a high tech company and made these claims in public without
even performing an accurate simulation or real world test. Stellarvue
declined to promote his products and we end up with this kind of
dribble from a disgruntled individual.
So, my point is still valid. Val, and for some reason Roland (who
should be far above all this immature nonsense), seem to have a
problem with a company producing very well made and well color
corrected ACHROMATS. Geez guys, get a life.
David
ValeryD
> Well said, David!
>
> I tell you, this is getting B-O-R-I-N-G!!!
I am boring too. Very much boring reading, hearing about tales, that
recently made achromats are nearly as perefect as ED APO are.
> Roland and Val, do you want to REALLY impress the amateur community? Okay,
> here's a challenge for ya - make an apo for US$1,000. Say a 4". Can ya do
> it? eh? Okay, maybe that's pushing it - try for $1500-1700 US. OTA only, we
> don't want to push our luck. Triplet is fine. How about at least 1/30 wave
> RMS error too.
FYI, Nobody can make 4" true APO with good optics for $1000.
What can be achieved by such modern manufacturers is peoples foolishing
using ED name, telling to novices that these new achromats has lack of
false colors etc etc.
> I get soooo tired of this assumptive bushwacking you boys are doing.
> Actually, in Roland's defense, he at least posts technical information of
> value - mostly accurate. Val - what are you doing, sir?!
What I doing? I try to serve amateurs needs at best I can. Some peoples,
who know well the truth about "modern ED achromats" already used our
color correctors with various achromats. They see the difference. It is
obvious.
About Roland's defense. I think he don't need your service at all. He
know enough, he has enough knowelege and what he doing is supply amateurs
by truly color corrected scopes. He dont sing any sweet false songs for
peoples who don't know whats going on. He doing a hard work to make their
APOs.
> Dismayed and disappointed...
Do you like an appointment? Please....Take one of these new miracle
achromats (say, 100mm F/7) and line up in near 4" Traveller. Your
appointment very quickly will change on a disappointment. The same will
be if you will line up a miracle 4" achromat vs Vixen 4" F/9 ED APO .
Valery Deryuzhin.
William Mc Hale
: William Mc Hale <wmc...@umbc7.umbc.edu> wrote in message news:<9pgj3j$sjc$1...@news.umbc.edu>...
:>
:> Dave,
: Bill:
While I know little about the politics amongst various manufacturers, I
did check the Stellarvue websit, it does claim that the 80mm schope will
outperform some ED scopes that are out there; now perhaps these ED scopes
are really simply that fake ED glass that Roland and mentioned, but
claiming to outperform an ED scope without reference to which particular
scopes does sort of make the claim of near Apo or semi-apo performance.
--
Bill
***************************************************************************
No one is listening until you make a mistake.
Darren Hennig
the work for your customers...
I'm ---- outta here! [did not miss SAA, and since seeing this, don't miss it
again!]
B.T.Marshall
1010 and compared to a 102ED F6.5 not F9. The wording in that post which you have retained in your response is that
the 1010 performed "nearly" as well regarding chromatic and other abberations. I think everyone understands the
subjectivity of such comparisons and this is after all the only meaningful comparison one can make in this hobby. As
such, it is always best to try before you buy. For myself, I have seen enough circumstantial evidence from posts by
numerous users of the 1010 and several now for the 102D to be very comfortable in giving it a go. What can I loose?
Vic Maris does provide a 30 day money back guarantee. And yes I have tried that out too on a pair of binoculars I
returned for which I was reimbursed full cost no questions asked. What can I gain? An excellent short tube 4 inch
achromat with excellent mechanicals backed up by excellent customer support and service for less than a grand. Hard
to beat that. Regards.
Tom.
Nick Zivanovic
"Peter Besenbruch" <prb.nonl...@product.lava.net> wrote in message
news:Vvi7Ox0N9gX2l1...@4ax.com...
> On Thu, 04 Oct 2001 03:45:38 GMT, "Darren Hennig"
> <dhen...@teluaplanet.net> wrote:
>
> >but in defense of the Stellarvue line,
>
> Who attacked Stellarvue? I haven't seen their name mentioned once
> by either Valery or Roland.
Peter, go back and look at the first post in this thread, and then Roland's
reply to it. It is pretty obvious who is being attacked, and yes, Valery did
mention Stellarvue *by name*. By Brian Tung's post in this thread, I think
he
figured it out as well.
Truth be told, a few weeks ago, Valery came on the Stellarvue e-group and
started making noise about how well the Chromacorr would work with the 102D
and
that Stellarvue should sell his product. Repeated attempts by Vic Maris to
take
his "negotiations" to private e-mail (where it belongs) failed. He went on
and
on, ignoring Vic, until he was shunned by the group and finally removed by
the
moderator (who is NOT Vic, by the way). Now, it appears he has a personal
vendetta against Stellarvue and uses every opportunity to bash them. That's
funny, because when got he started on the e-group, he was praising them.
Hmmm.
What changed Val? Didn't get your way?
I have an AT1010 (80mm f/6) and I had the opportunity to use a 102D for a
week.
Both are well made, and well corrected Achromats. Both are marketed as such.
Any
claims for ED-like performance in the 102D come directly from the owners of
these scopes, and Stellarvue, like every other manufacturer out there, uses
these testimonials on their web site.
I will go on the record now and state that the 102D has very little false
color.
I've used it. Under a variety of observing conditions, with magnifications
ranging from 18x to 235x. With no color blindness (I just had a
comprehensive
eye exam a month ago). Is it an apochromat? No. But color on bright objects
(Jupiter, the moon, Vega) is very, very minimal, and *almost* disappears
with
careful focusing (something made easy by the very high quality mechanicals
of
this scope). No more than the color in a CR150+Chromacorr as referenced by
this
review in the Refractors e-group:
http://groups.yahoo.com/group/Refractors/message/6912
The scope is sharp to the edge of the field, shows no astigmatism, no zones,
and
the star test is textbook. Also, in the above review, the author talks of
the
various tweaks he used to minimize the false color on his scope+CC. In the
102D,
no tweaking was necessary; all I did was pop in an eyepiece.
Is there false color? Yes. Is it acceptable? Yes. Roland says the best
possible
correction in an achromat using normal glasses is 1 part in 2000. Is this
what
I'm seeing? Very likely. Is it what you see in the Synta refractors? No. Why
is
it so hard to believe that a manufacturer that is obsessed with producing
such a
fine product and individually tests EVERY single one can produce a scope at
the
theoretical limits of performance? Do you think Synta does this? People that
have been exposed in the last few years to the flood of imported achromats
believe that this is the way a properly made achromat should perform, and
assocate that performance with Roland's "1 part in 2000" figure. Is it so
hard
to believe that these cheaply produced scopes (on average) may not simply
meet
that theoretical limit?
Nick Zivanovic
Chris1011
besides, they are not cheap!>>
What??? I don't get it. What are you trying to say that I said?? I've made no
cheap shot at the chromacorr - nowhere was a cheap shot even intended.
Roland Christen
JMc
that some of the 80 mm f/6s, were actually 60 mm f/8s because of focus
tube vignetting. That may explain the better color correction that some
are claiming vs. the standard short tube offerings.
Jim McSheehy
> Dave wrote:
> Stellarvue has
> never claimed that the 80mm f6 or the 102D or 102EDT is an APO. There
> is no conspiracy here, unless there's one between yourself and Roland.
> There are no false claims being made by Stellarvue, no promotion of
> "miracle achromats", no false dreams of a cheap apo, no claim of
> completely eliminating color, and not even one claim of being a
> "semi-apo"...whatever that is (ask William Yang, maybe he knows).
>
[...]
Chris1011
should be far above all this immature nonsense), seem to have a
problem with a company producing very well made and well color
corrected ACHROMATS. Geez guys, get a life.>>
I have no issue at all about any one company. My intent is to explain how
achromats and apos differ. if you don't understand that, well, I can't help
you.
Roland Christen
Chris1011
No, I don't need to prove anything, I just want to make a living in this
business.
>> Okay,here's a challenge for ya - make an apo for US$1,000. Say a 4". Can ya
do
it? eh? Okay, maybe that's pushing it - try for $1500-1700 US. OTA only, we
don't want to push our luck. Triplet is fine. How about at least 1/30 wave
RMS error too.>>
Sorry, the up front cost for high quality glass would make this venture
unprofitable. What's the point anyway? How could a 4" refractor impress the
majority of the amateur community? Now a 20" for that price might be
impressive, yes?
Roland Christen
Nick Zivanovic
news:3BBC8460...@mydeja.com...
> There was a long thread some months ago about these scopes, and it seems
> that some of the 80 mm f/6s, were actually 60 mm f/8s because of focus
> tube vignetting. That may explain the better color correction that some
> are claiming vs. the standard short tube offerings.
>
> Jim McSheehy
Sorry, Jim, but that is old news and has long since changed. The AT1010 (2"
version) has no vignetting, and the AT1002 (1.25" version) was redesigned
with a shorter drawtube to minimize this. The 102s, being 2" also, do not
have an issue with this.
It is amazing that this keeps getting rehashed here. Regarding the "standard
short tube offerings", check out an ST80 sometime. You'll find the same
issue of the focuser drawtube vignetting the light cone, and they've done
nothing about it.
Nick Zivanovic
Dave
Roland:
Please clarify this statement:
"NO, there is no range of achromat color correction. Achromats are
made from
> ordinary glasses that have no special dispersion characteristics. An achromat
> is made with a crown positive element and a flint negative element."
So, any scope that has ED glass in it is not an achromat???? Are you
saying that all achromats are made from the same glass type??? Does
lens coatings make any difference at all this equation? So, any scope
that possesss an ED glass is not an achromat? So, the TV Ranger and
Pronto, which contain ED glass are not achromats. Then why do I see
color in a TV Ranger, Pronto, and TV-85? They aren't achromats because
"Achromats are made from ordinary glasses" but their performance is
not APO. Can we all agree to call them "Semi-apo's"?? Would you like
to propose a definition of semi-apo? Maybe then we can better define
what any scope should be classified as... achromat, semi-apo, apo. I'm
all for that.
David
Chris1011
So, any scope that has ED glass in it is not an achromat????>>
Well, there is ED glass and then there is "fake ED " glass - specifically FK5,
which some manufacturers classify as an ED glass, but which really produces
only achromat correction of color. So, yes, there can be an "ED" lens that is
only an achromat.
>> Are you saying that all achromats are made from the same glass type???>>
No, of course not. You can make an achromat out of any combination of over 2000
glasses that are listed in the various glass catalogs, and yes indeed they will
all have the same color correction. To get meaningful color correction, you
need to use one of the half dozen special glasses that are based on fluoride
compounds.
>> Does lens coatings make any difference at all this equation?>>
No. There is zero difference no matter what you coat a glass with. Unless you
coat it with an aluminum layer, in which case you have a mirror, and no more
color error.
>>So, any scope that possesss an ED glass is not an achromat? >>
See my first statement. It is quite possible to make an achromat using ED
glass, yes indeedy. Not every ED lens can be called an apo.
Roland Christen
Stephen Pitt
This is a perfect point to stop and ask the question, Roland: Has Stellarvue
called any
element in their 102D doublet *ED*?
I think its time to stop blurring the line of reasonableness, don't you?
Aligning yourself
with Valery in this thread and rehashing FK5 without end does nothing to
enhance your credibility.
The first question is the only one in this petered-out thread that demands to
be answered.
Best regards, Stephen Pitt
>
> Roland Christen
--
Posted from ip-89-046.riv.pe.net [64.38.89.46]
via Mailgate.ORG Server - http://www.Mailgate.ORG
ValeryD
Dave,
> This is simply not a true statement. They are not advertised as such
> and Val and Roland know that.
I just commented an observation and did't say that the company you
mentioned claims APO performance in their achromats.
If I remember, some vocal observers reports (and companies use these
reports) something like this " at star-party XX our model ZZ
stayed
very close to TV-102 etc.
These companies claims "semi-apo" performance of their scopes,
"lack of colors" , "new formula" etc etc. Their fantasy really
don't know any limit.
>Val has an issue with Stellarvue in that he wanted Stellarvue to
>promote his chromacor.
No promotion necessary at all. I just let peoples know, that if
their scopes are C-F achromats, then they will work with Chromacor
at the level when no color will be seen at all.
>Val came on to the stellarvue groups site and announced that he had
>run some simulations on a computer and that the chromacor would
eliminate >false color on the 102D.
This is true, but I didn't asked about promotion at all.
>The incredible thing about it was that he had not tested it
> with the acutal scope. His "simulation" is worthless because he does
> not know the optical characteristics of the 102D lens (he didn't even
> know that it was a f6.9, doesn't know what glass is used or which
> wavelengths need "correction"), etc, etc.
If only you ever knew optics enough to be able to reasoning about THIS
subject, then, I believe, this your post will never been typed.
If your memory serves you well, you my remember, that I underlined,
that
this will be valid in the case if a given objective is close to
classical
C-F correction (the best compromise).
And for such simulation I don't need to know a glass formula. C-F
achromat
is a C-F achromat. Roland already explained, that ALL achromats will
have
the same secondary spectrum if their D and F/D are the same - no
matter
which standard glasses will be used.
>From an optical engineer's perspective, this was completely
unprofessional.
You think so? If yes, then you are mistaken. We tested a Chromacor on
some
different achromats and the results were exactly according to our
simulations.
It was in the case with 70mm F/7 achromat as well as with 10" F/6.5
and
many between.
>He'd be fired if he worked for a high tech company and made these
>claims in public without even performing an accurate simulation or
>real world test.
See above.
> Stellarvue declined to promote his products and we end up with
>this kind of dribble from a disgruntled individual.
Again. Nobody was asked about promotion.
> So, my point is still valid. Val, and for some reason Roland (who
> should be far above all this immature nonsense), seem to have a
> problem with a company producing very well made and well color
> corrected ACHROMATS. Geez guys, get a life.
LOLT!
Just these months we will finish five 8" F/8 achromats with Chromacors
pre-installed on a special flip-flop mounting inside a tube. This
scope
can be used in two modes: "Achromat" and "Corrector-in" .
Three of these scopes were sold far before they were began!
About "problems" with manufacturing of "well color corrected
ACHROMATS".
A while ago the AP made many small achromats (for guide scopes? ).
I heard some responces about them. They are quite good. But this does
not force Roland to claim that his achromats has "lack of colors" or
that
that made under "new formula" etc.
You need to know also, that SV does not produce their optics at all.
Optics just selected from large batch made overseas in Far East.
Also, not the ARIES, not the AP was a discoverers of a new method
of manufacturing of "well color corrected ACHROMATS" - an internal
aperture stop! And why _internal_ ??? To hide this method from
customers!
Now, I believe, you have a clue who has a problems with color
correction.
Finally. FYI, we already developed a small ( 10mm diameter!) Barlow
lens 1.7x which will correct a false colors to insignificant level
in such achromats like 70mm F/5-7 , 80mm F/5-7 and to very low level
in
100mm F/5-7 .
Lets hope, that SV scopes, according to your guess, has too
different
design from classical achromats and this lens will not work in their
scopes. This will be much better for their potential competitors.
(Apple vs Intel story).
Valery Deryuzhin.
Stephen Pitt
> There was a long thread some months ago about these scopes, and it seems
> that some of the 80 mm f/6s, were actually 60 mm f/8s because of focus
> tube vignetting. That may explain the better color correction that some
> are claiming vs. the standard short tube offerings.
>
> Jim McSheehy
Jim: Stellarvue corrected the problem immediately and publicly. However, the
guy who
sells $750 light cone masks still masks on, incites and dupes the naive with
endless
tirades on mythology, and calls his competitions' pots black.
Not too even-handed, I say.
Best regards, Stephen Pitt
>
>
> > Have you compared an 80mm F6 Stellarvue to a Vixen ED?
Chris1011
This is a perfect point to stop and ask the question, Roland: Has
I know nothing about Stellarvue or their products. I do know other companies
that advertised scopes made with FK5 that they called "ED" scopes.
I also know what is possible and what is not possible in optics.
There is a place for fine achromats in amateur astronomy. I have a very nice
80mm F11 scope that I would put up against any other achromat, long or short.
It shows little if any obvious color on the Moon, planets and even Vega. It
performs beautifully up to 250x on the planets and I've even taken it up to
500x on doubles. I have elongated 0.8 arc sec equal magnitude doubles with this
scope. However, it is not an apo, nor would I ever claim that it has apo-like
performance. If I were to image with it, it would certainly show in nice blue
halos around bright stars on film.
Roland Christen
Nick Zivanovic
"ValeryD" <ar...@mercury.kherson.ua> wrote in message
news:5c4a4ee7.01100...@posting.google.com...
>>[David Owen said:]
> >Val has an issue with Stellarvue in that he wanted Stellarvue to
> >promote his chromacor.
>
>[Valery:]
> No promotion necessary at all. I just let peoples know, that if
> their scopes are C-F achromats, then they will work with Chromacor
> at the level when no color will be seen at all.
>
>> [David:]
> >Val came on to the stellarvue groups site and announced that he had
> >run some simulations on a computer and that the chromacor would
> eliminate >false color on the 102D.
>
> [Valery:]
> This is true, but I didn't asked about promotion at all.
OK, Val, then what is this? I quote you in message
(http://groups.yahoo.com/group/Stellarvue/message/2347) :
>>>>>
"I need to note, that a while ago, when the Chromacor project was
only on experimental stage, we spoke with Vic about possibilities
to use this device in SV scopes. At that time, when far not all
was clear with Chromacor project, we agreed, that it will be
necessary to reach a stable manufacturing of Chromacor before we
will come back to discuss any possibilities to use a Chromacor
with SV scopes.
IMO, now is a right time to look in a perspective. And successfull
Chromacor testing with other scopes give us a good hope, that
this unique device, developed in our ARIES Co., will work just
fine with famouse SV scopes.
As many times were said, it is quite important to have a nice,
well corrected achromat with smooth optics for final success in
using it with Chromacor. And, as I was fully convinced, SV scopes
has objectives which exactly meet these requirements.
I hope, that Vic will consider the possibility to come back to
discuss this theme again, but with practical base under it."
>>>>>
Sounds like asking about promotion to me. And what about this one
(http://groups.yahoo.com/group/Stellarvue/message/2350):
>>>>>
"--- In Stellarvue@y..., vic@s... wrote:
> Valery:
>
> So send me one, I will test it and I will send it around to the
focus
> group to test also. We can publish the results here.
>
> Vic Maris
Vic,
Let go another way (appoved with Synta refractors). You can ship
to us a scope you are interested in further selling with Chromacor.
Having enough very special equipment, we will test all here and
will properly match a Chromacor (according necessary spherical
correction) to keep original spherical correction intact.
We can also machine necessary interface for star-diagonal and
Chromacor to keep all aberration at best possible control.
Then all will be shipped to you for final testing and possible
promotion."
>>>>>
Oh, OK, you were talking about Vic's promoting it, not yours. I get it.
(Note that Val brought up the whole issue of SV+CC, not Vic.)
So Valery, care to retract the statement that "I didn't asked about
promotion at all"?
The readers here are free to go to the SV e-group and read the whole
exchange for themselves. It will then become very clear what this thread is
really about.
Nick Zivanovic
Mike Burley
To be completely accurate, Val ran some computer simulations indicating
the Chromacor might correct chromatic aberration in the Stellarvue 102D
(achro) if it had standard C-F correction. He suggested Vic Maris ship
one so he could match a Chromacor to it and send it back to him for
testing. Mr. Maris seemed interested at first then later declined,
stating the Chromacor would not work with his scopes without explanation
as to why this was so. It seems that neither Valery or Vic really know
if the Chromacor will work or not since this scope combo wasn't tested
by either man. I think this outcome was unfortunate, as this
Stellarvue/Chromacor combo has potential at the very least.
Mike in Oregon
<SNIP> > Val has an issue with Stellarvue in that
Nick Zivanovic
"Mike Burley" <mbu...@teleport.com> wrote in message
news:3BBCA6F5...@teleport.com...
>
> To be completely accurate, Val ran some computer simulations indicating
> the Chromacor might correct chromatic aberration in the Stellarvue 102D
> (achro) if it had standard C-F correction. He suggested Vic Maris ship
> one so he could match a Chromacor to it and send it back to him for
> testing. Mr. Maris seemed interested at first then later declined,
> stating the Chromacor would not work with his scopes without explanation
> as to why this was so.
To be *completely* accurate, Mike, Vic never said such a thing. In fact, in
message (http://groups.yahoo.com/group/Stellarvue/message/2373) he said:
"4. I will not state that the Ch will have no benefit until I test
one. Also, I would not make a claim that the Ch will work with the
Stellarvue. How would I know? How would Val know? Why does the
ongoing post state this?"
Again, I ask those that continue to argue this from a point of supposition
to go to the Stellarvue e-group and read the words straight from the horses'
mouths.
Nick Zivanovic
Brian Tung
> Peter, go back and look at the first post in this thread, and then Roland's
> reply to it. It is pretty obvious who is being attacked, and yes, Valery did
> mention Stellarvue *by name*. By Brian Tung's post in this thread, I think
> he figured it out as well.
You misinterpret me, actually. I wouldn't post this, but in case anyone
thinks I meant Stellarvue, I want to make it clear I don't.
Brian Tung <br...@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
Mike Burley
How do you know? This was a review of a Synta/Chromacor combo, not a
comparison with a Stellarvue 102! Did you write the review? I don't
doubt the Stellarvue's are well made but I, for one am not interested in
wild speculation.
Mike in Oregon
Nick Zivanovic wrote in part:
<SNIP>
Nick Zivanovic
"Brian Tung" <br...@zot.isi.edu> wrote in message
news:9pi9mi$u1$1...@zot.isi.edu...
> Nick Zivanovic wrote:
> > Peter, go back and look at the first post in this thread, and then
Roland's
> > reply to it. It is pretty obvious who is being attacked, and yes, Valery
did
> > mention Stellarvue *by name*. By Brian Tung's post in this thread, I
think
> > he figured it out as well.
>
> You misinterpret me, actually. I wouldn't post this, but in case anyone
> thinks I meant Stellarvue, I want to make it clear I don't.
Thank you for the clarification Brian. Please accept my apologies for making
the inference.
Nick Zivanovic
Nick Zivanovic
Mike,
I am referring to the obvious visible color in that combination as stated by
the writer. He said it was slight but noticeable. This directly contradicts
Valery's claim that the CC eliminates color and can turn a Synta into an
APO. I saw the same (subjective I admit) level of correction in the 102D
with my own eyes. I did write a review of my experiences with the 102D,
available on the SV e-group. Slight, but noticeable. I never said the 102D
was color free, something that Val has stated many times about the
combination referenced in the above review.
Nick Zivanovic
Mike Burley
Im splitting hairs here, but the AT1010 still does vignette slightly,
having 72 to 78mm clear aperture. I assume this has to do with focuser
tube positioning with various ep's. Check the Stellarvue web site:
http://www.stellarvue.com/specifications.html
Mike in Oregon
Isaac Newton
Bwahahahahahahahahahahahahahahahahahahahaha.
Mike Burley
I follow the Stellarvue mailing list on a daily basis. Vic did say that
- I remember it distinctly. But you're correct, that it isn't all he
said.
Mike in Oregon
ValeryD
Nick,
With all respect I need to tell you - all what you said above about
equal colors in 80mm F/6 and 150mm Synta + Chromacor is complete
nonsense.
A blue light in 150mm Synta + Chromacor corrected 6x better than in
stock objective. Longitudinal aberration for blue 486nm ligh is only
0.09mm. This is about 1/13000 of a focal length.
Same with red light.
In a 80mm F/6 achromat a longitudinal aberration for blue and red
light is about 0.24mm.
You own perception is not solid enough base to judge about color
relative correction in scopes. You can be less sensitive to blue-violet,
you have your own subjective point of view what does it mean "minimal"
colors and what does it mean "almost disappear" etc. You can be also
a biased, and IMO, you really are.
Valery Deryuzhin.
Mike Burley
Your misrepresenting what Valerys performance claims are. The Synta
120/Chromacor is color free. The 150/Chromacor has some deep
purple/violet with Venus or Sirius & Vega. Still, I doubt any achro will
hold a candle to it.
Mike in Oregon
ValeryD
> I'm the original poster of the message you are refering to. The person who posted this message had just received her
> 1010 and compared to a 102ED F6.5 not F9. The wording in that post which you have retained in your response is that
> the 1010 performed "nearly" as well regarding chromatic and other abberations. I think everyone understands the
> subjectivity of such comparisons and this is after all the only meaningful comparison one can make in this hobby. As
> such, it is always best to try before you buy. For myself, I have seen enough circumstantial evidence from posts by
> numerous users of the 1010 and several now for the 102D to be very comfortable in giving it a go. What can I loose?
> Vic Maris does provide a 30 day money back guarantee. And yes I have tried that out too on a pair of binoculars I
> returned for which I was reimbursed full cost no questions asked. What can I gain? An excellent short tube 4 inch
> achromat with excellent mechanicals backed up by excellent customer support and service for less than a grand. Hard
> to beat that. Regards.
>
> Tom.
Tom,
Even Vixen 102 F/6.5 has at least 5x better color correction (5x smaller
secondary spectrum) than any 102mm F/6.9 achromat even if this achromat
was designed by God.
Also, note, that nobody questioned these small achromats optics quality -
a selection makes its deal, their mechanical quality.
The question is color correction issue. Any statement like "our scopes
has lack of colors", "new scopes will be more color free because they
will be made under NEW FORMULA" , "semi-APO" etc etc aimed only to
customers ears with intention to foolish them.
Achromats will always remain achromats. Can you all finally understand this?
Valery Deryuzhin.
RichardN22
It takes two to tango. If you didn't constantly reply to these threads they
would die a quick death.
richard
Nick Zivanovic
>
> Nick,
>
> With all respect I need to tell you - all what you said above about
> equal colors in 80mm F/6 and 150mm Synta + Chromacor is complete
> nonsense.
> A blue light in 150mm Synta + Chromacor corrected 6x better than in
> stock objective. Longitudinal aberration for blue 486nm ligh is only
> 0.09mm. This is about 1/13000 of a focal length.
> Same with red light.
>
> In a 80mm F/6 achromat a longitudinal aberration for blue and red
> light is about 0.24mm.
>
> You own perception is not solid enough base to judge about color
> relative correction in scopes. You can be less sensitive to blue-violet,
> you have your own subjective point of view what does it mean "minimal"
> colors and what does it mean "almost disappear" etc. You can be also
> a biased, and IMO, you really are.
>
>
> Valery Deryuzhin.
Valery,
You didn't read my post. I did not mention an 80mm f/6. I was talking about
the SV 102D (102mm f/6.9) that you were trying to convince Vic to send you.
My mention of the other article (yes I know it was a different scope) was to
show that the reviewer saw some false color on the 150+CC. I saw some false
color on the 102D.
My inference here is that the 150+CC combination does not totally eliminate
false color, but vastly improves it (I'll give you that). The amount of
color I see in the 102D is less than other 4" achromats I've looked through.
What does minimal mean to me? So little color that it is totally
unobjectionable. What does almost disappear mean? It means that when the
focus was carefully tweaked, the color was nearly imperceptible. Visually.
On Vega. On the moon, there is a slight magenta fringe on the limb. On
Jupiter the same, but at times nearly invisible. This is all based on visual
only (and my eyes are very sensitive in the blue-violet range -- I see very
vivid false color on other achromats). With regard to my being biased, I
guess I am. I am the happy owner of a Stellarvue scope, and have 2 more on
order. I'm also the happy owner of an 18" Obsession with premium figured
optics (so I know what color-free is), an active amateur OBSERVER in a large
club, and I've looked through numerous instruments from Synta ST80s to
Astro-Physics apos and can see the various amounts of color correction in
them.
Nick Zivanovic
Nick Zivanovic
nz
"RichardN22" <richa...@aol.comeatcaca> wrote in message
news:20011004154310...@mb-fo.aol.com...
Rockett Crawford
Doesn't anyone know of any "true myths" about achromats??
Rockett
Capella's Obsservatory
http://www.jestercourt.com/~capella
Ron B[ee]
on the Stellarvue telescope, he can simply order one (or several)
as he did with the 150mm Synta and 120mm Synta. Why should
someone else be burdened with the expense of making the scope
available free of charge (even for a limited time use) when the
financial benefit will go to Aries. Finally, publish the result and
market the Chromacor.
Alternatively, as I've said many times in the past, Valery can
also send a Chromacor to Ed Ting or Todd Gross whom I'm
sure have access to so many scopes.
Personally, I believe computer simulation is certainly a good start,
but not an end all. The proof is actually in the real-world "pudding
of seeing" ;-) as there are so many variables involved.
Just my 102 opinions.
Ron B[ee]
-----------
"Mike Burley" <mbu...@teleport.com> wrote in message
news:3BBCA6F5...@teleport.com...
Chris1011
Personally, I believe computer simulation is certainly a good start,
but not an end all.>>
Computer simulation is as good as it gets, far better than subjective "eyeball"
guestimates. For instance, the computer simulation for a particular design says
that at 430nm the color halo will be 150 microns, and by golly, when you
actually run light through it and take an image at 430nm, you somehow get 150
microns.
You have to understand that these programs were not developed by dummies, and
that the whole science of optics has been peer reviewed for more than 150 years
by people far more knowledgeable than myself or Valery or ...
The whole giant optical industry all over the world is based on this science,
and yes inddeee it does work, so unless you really know the ins and outs of
optics, there is no point in making statements like: "computer simulation is
certainly a good start, but not an end all".
Roland Christen
Chris1011
Ah, but is this not more interesting than pyramids and numerology? There's
actually some facts being presented, or maybe that's out of fashion these days?
Roland Christen
Lugosi
news:5c4a4ee7.01100...@posting.google.com...
> Really, it is almost fun to see such claims - " THIS achro is almost
same
> good as APO", "THIS optics is1/63 wave" etc etc, but only if one
forgot,
> that peoples pay their hardly earned money for these myths.
> They always have alternatives, but such myths "gravitate" them
constantly.
It's nice to get the full story, yes, but this is the same kinda thing
with advertising everywhere. The idea is to do everything you can to
sell without crossing the line into palpable fraud, and the vagueness of
the term "misleading" means you can get away with a lot if you *very*
carefully word your ad copy.
/John -- saving up for an apo
Ron B[ee]
...snip...
> The whole giant optical industry all over the world is based on this
science,
> and yes inddeee it does work, so unless you really know the ins and outs
of
> optics, there is no point in making statements like: "computer simulation
is
> certainly a good start, but not an end all".
>
> Roland Christen
Thanks for the corrections and I stand corrected.
Ron B[ee]
RichardN22
"eyeball"
guestimates. For instance, the computer simulation for a particular design says
that at 430nm the color halo will be 150 microns, and by golly, when you
actually run light through it and take an image at 430nm, you somehow get 150
microns.>>
Yeah, but Roland, then when you pay the money for a high end computer tested
and certified scope, and you don't like the images, you have to blame your own
eyes! It's much easier to blame the manufacturer. ;-)
Richard Navarrete
Richa...@aol.com
Astrophotography Web Page - http://members.aol.com/richardn22
Ron B[ee]
software that was tested in a computer simulator, simulating a new
microprocessor without ever running on the real microprocessor now,
would you ;-)?
Ron B[ee]
"Chris1011" <chri...@aol.com> wrote in message
news:20011004163137...@mb-mv.aol.com...
> >>
Stephen Pitt
> relative correction in scopes. You can be less sensitive to blue-violet,
> you have your own subjective point of view what does it mean "minimal"
> colors and what does it mean "almost disappear" etc. You can be also
> a biased, and IMO, you really are.
>
>
> Valery Deryuzhin.
Valery, your chromacorr, by virtue of it's 30mm clear aperature cuts at least
12-13mm into the light cone.
How much chromatic aberration is reduced by this masking, and how much is
reduced by the
content of the glass?
If the chromacorr changes the focal ratio from 150/1200 (f8) to 100/1200 (f12)
the amount of colour
will be equal to any other f12 achromat.
Regards, Stephen Pitt
--
Posted from ip-88-048.riv.pe.net [64.38.88.48]
via Mailgate.ORG Server - http://www.Mailgate.ORG
Brian Tung
> Ah, but you guys wouldn't wanna get on the plane that has an auto pilot
> software that was tested in a computer simulator, simulating a new
> microprocessor without ever running on the real microprocessor now,
> would you ;-)?
No, but on the other hand I don't believe you are really serious. There
are human factors involved in flying a plane that are not totally well
understood (if by "flying a plane" we include takeoff and landing). On
the other hand, the science of optics is very well understood. Calling
it a simulation is slightly misleading--a better term would be computer
aided analysis and design. True, it's not a "real" lens, but the term
"simulation" in many contexts carries a connotation of statistical tests
on numerous sample paths, and that's not really what is meant here.
But you're right, I would insist on human pilots, thank you. :)
Stephen Pitt
Hi, Rockett!
It would be a "True Lie" if I did.
Best regards,
Sue_and_Alan_French
That's pretty funny, coming from you. When it comes to telescopes you
really botched things up. First you did a misguided experiment and
mistakenly concluded there was no way to correct for the color dispersion in
a lens, delaying the development of the achromat by about 75 years. Then
the reflector you made was so poor it sat on a shelf gathering dust and it
was another 50 years before Hadley finally made a good one.
Clear skies, Alan
"Isaac Newton" <ap...@gravity.com> wrote in message
news:3BBCAE70...@gravity.com...
Bill Foley
build an automatic transmission factory in Warsaw....
Roland, remember:
Illegitimus non Carborundum.....
--
Clear, Dark Skies
Bill Foley
Dave
> >>
> So, any scope that has ED glass in it is not an achromat????>>
>
> Well, there is ED glass and then there is "fake ED " glass - specifically FK5,
> which some manufacturers classify as an ED glass, but which really produces
> only achromat correction of color. So, yes, there can be an "ED" lens that is
> only an achromat.
>
> >> Are you saying that all achromats are made from the same glass type???>>
>
> No, of course not. You can make an achromat out of any combination of over 2000
> glasses that are listed in the various glass catalogs, and yes indeed they will
> all have the same color correction. To get meaningful color correction, you
> need to use one of the half dozen special glasses that are based on fluoride
> compounds.
>
> >> Does lens coatings make any difference at all this equation?>>
>
> No. There is zero difference no matter what you coat a glass with. Unless you
> coat it with an aluminum layer, in which case you have a mirror, and no more
> color error.
>
> >>So, any scope that possesss an ED glass is not an achromat? >>
>
> See my first statement. It is quite possible to make an achromat using ED
> glass, yes indeedy. Not every ED lens can be called an apo.
>
> Roland Christen
Roland:
Thank you for your clear response. I honestly appreciate it very much.
David
rande...@home.com
who embellish and owners who don't know or who claim performance
levels clearly not produced by the scope in question.
Some problems are:
1. Put too much emphasis on one aberration while conveniently ignoring
others.
-example; Promoting the colour correction of a fast apo while
ignoring possibly serious spherical aberration effects.
2. Use clever marketing jargon, completely vague and unqualified to
push scopes in an effort to trick unwary buyers.
-example; "Performs like "X" scopes of much larger size."
3. Promote one positive aspect of a scope (either optical or
mechanical) while downplaying negative characteristics..
-example; "Imagine, a huge 8" Dob for only $499!"
Meanwhile, the mount is a piece of junk.
4. Claim near colour-free images while the scope demonstrates the
complete opposite to an unbiased source.
What you have working are two things; Pride and greed.
-Rich
rande...@home.com
it.
Then the apo hit the fan.
-Rich
On Thu, 04 Oct 2001 10:46:40 -0500, JMc <tri...@mydeja.com> wrote:
>There was a long thread some months ago about these scopes, and it seems
>that some of the 80 mm f/6s, were actually 60 mm f/8s because of focus
>tube vignetting. That may explain the better color correction that some
>are claiming vs. the standard short tube offerings.
>
>Jim McSheehy
>
>> Dave wrote:
>
>> Stellarvue has
>> never claimed that the 80mm f6 or the 102D or 102EDT is an APO. There
>> is no conspiracy here, unless there's one between yourself and Roland.
>> There are no false claims being made by Stellarvue, no promotion of
>> "miracle achromats", no false dreams of a cheap apo, no claim of
>> completely eliminating color, and not even one claim of being a
>> "semi-apo"...whatever that is (ask William Yang, maybe he knows).
>>
>
>[...]
>
>
>> Have you compared an 80mm F6 Stellarvue to a Vixen ED?
Chris1011
Well that makes me feel better for living.
Roland Christen
Dave
> "Darren Hennig" <dhen...@teluaplanet.net> wrote in message news:<CXQu7.65170$9j.81...@news1.telusplanet.net>...
> > Well said, David!
> >
> > I tell you, this is getting B-O-R-I-N-G!!!
>
> I am boring too. Very much boring reading, hearing about tales, that
> recently made achromats are nearly as perefect as ED APO are.
>
>
>
> > Roland and Val, do you want to REALLY impress the amateur community? Okay,
> > here's a challenge for ya - make an apo for US$1,000. Say a 4". Can ya do
> > it? eh? Okay, maybe that's pushing it - try for $1500-1700 US. OTA only, we
> > don't want to push our luck. Triplet is fine. How about at least 1/30 wave
> > RMS error too.
>
> FYI, Nobody can make 4" true APO with good optics for $1000.
> What can be achieved by such modern manufacturers is peoples foolishing
> using ED name, telling to novices that these new achromats has lack of
> false colors etc etc.
>
>
> > I get soooo tired of this assumptive bushwacking you boys are doing.
> > Actually, in Roland's defense, he at least posts technical information of
> > value - mostly accurate. Val - what are you doing, sir?!
>
>
> What I doing? I try to serve amateurs needs at best I can. Some peoples,
> who know well the truth about "modern ED achromats" already used our
> color correctors with various achromats. They see the difference. It is
> obvious.
>
> About Roland's defense. I think he don't need your service at all. He
> know enough, he has enough knowelege and what he doing is supply amateurs
> by truly color corrected scopes. He dont sing any sweet false songs for
> peoples who don't know whats going on. He doing a hard work to make their
> APOs.
>
>
>
> > Dismayed and disappointed...
>
> Do you like an appointment? Please....Take one of these new miracle
> achromats (say, 100mm F/7) and line up in near 4" Traveller. Your
> appointment very quickly will change on a disappointment. The same will
> be if you will line up a miracle 4" achromat vs Vixen 4" F/9 ED APO .
>
>
> Valery Deryuzhin.
Val:
Other than being an obnoxious, why do you keep insisting on using the
term "miracle achromats"? Would you like for everyone to start calling
your chromacor a "miracle vignetting aperture mask"?
I know that it isn't and that to call your chromacor this name would
be incorrect. So why do you continue to make such an ass out of
yourself?
David
Dave
>
> Dave,
>
>
> > This is simply not a true statement. They are not advertised as such
> > and Val and Roland know that.
>
> I just commented an observation and did't say that the company you
> mentioned claims APO performance in their achromats.
------------------------------------
No, you claimed that the manufacturer of this scopes makes "miracle
achromats".
--------------------------------------------------
>
> If I remember, some vocal observers reports (and companies use these
> reports) something like this " at star-party XX our model ZZ
> stayed
> very close to TV-102 etc.
>
> These companies claims "semi-apo" performance of their scopes,
> "lack of colors" , "new formula" etc etc. Their fantasy really
> don't know any limit.
-----------------------------
There is no fantacy, except that which resides in your head. These
reports are from observers that have used these scopes. You've never
even seen one and you still make these absurd remarks. Show me where
the company claims "semi-apo performance". See, you put words in the
mouths of others to prove your point.
>
------------------------------
>
> >Val has an issue with Stellarvue in that he wanted Stellarvue to
> >promote his chromacor.
>
> No promotion necessary at all. I just let peoples know, that if
> their scopes are C-F achromats, then they will work with Chromacor
> at the level when no color will be seen at all.
>
----------------------------
No, you continue to lie. See posting by Nick Z. with actual postings
you made yourself. I won't repeat them all here, I'd end up with a
book!
-0-------------------------------------
>
> >Val came on to the stellarvue groups site and announced that he had
> >run some simulations on a computer and that the chromacor would
> eliminate >false color on the 102D.
>
> This is true, but I didn't asked about promotion at all.
>
>
-----------------------------
No, you lie again...(gosh, is there a pattern developing here?). See
above.
---------------------------------------
> >The incredible thing about it was that he had not tested it
> > with the acutal scope. His "simulation" is worthless because he does
> > not know the optical characteristics of the 102D lens (he didn't even
> > know that it was a f6.9, doesn't know what glass is used or which
> > wavelengths need "correction"), etc, etc.
>
> If only you ever knew optics enough to be able to reasoning about THIS
> subject, then, I believe, this your post will never been typed.
-----------------------
I do know a lot about it and would write it again without any problem
at all. You don't even know who I am or anything about me and you make
such a claim?
------------------------------
>
> If your memory serves you well, you my remember, that I underlined,
> that
> this will be valid in the case if a given objective is close to
> classical
> C-F correction (the best compromise).
> And for such simulation I don't need to know a glass formula. C-F
> achromat
> is a C-F achromat. Roland already explained, that ALL achromats will
> have
> the same secondary spectrum if their D and F/D are the same - no
> matter
> which standard glasses will be used.
----------------------------
You assume that "standard" glass is being used. You are wrong. And no,
again, you did not underline that this would be the case if a standard
classical C-F correction was needed. You flat out stated that you had
performed a simulation and announced that your chromacor would
eliminate false color in the 102D. Period.
-------------------------------
>
>
> >From an optical engineer's perspective, this was completely
> unprofessional.
>
> You think so? If yes, then you are mistaken. We tested a Chromacor on
> some
> different achromats and the results were exactly according to our
> simulations.
> It was in the case with 70mm F/7 achromat as well as with 10" F/6.5
> and
> many between.
>
-------------------------------------
I am not mistaken. Any Professional Engineer making such claims
without a well executed and factual based computer simulation
representing the many complexities of an optical system would be fired
by a well run organization if such claims were publically presented as
being factual. But then this is America, the same rules do not apply
where you are from.
-----------------------------------
>
> >He'd be fired if he worked for a high tech company and made these
> >claims in public without even performing an accurate simulation or
> >real world test.
>
> See above.
>
------------------------------
Yes, please do see above.
------------------------------------
>
> > Stellarvue declined to promote his products and we end up with
> >this kind of dribble from a disgruntled individual.
>
> Again. Nobody was asked about promotion.
>
-----------------------------------
More lies, yes you did, see above reference re: Nick Z. posts.
-------------------------------------
>
>
> > So, my point is still valid. Val, and for some reason Roland (who
> > should be far above all this immature nonsense), seem to have a
> > problem with a company producing very well made and well color
> > corrected ACHROMATS. Geez guys, get a life.
>
> LOLT!
>
--------------------------
:) I can smile too!
------------------------------
> Just these months we will finish five 8" F/8 achromats with Chromacors
> pre-installed on a special flip-flop mounting inside a tube. This
> scope
> can be used in two modes: "Achromat" and "Corrector-in" .
> Three of these scopes were sold far before they were began!
>
-------------------------------
Congratulations, I guess. What's that got to do with anything??
-----------------------------------
>
> About "problems" with manufacturing of "well color corrected
> ACHROMATS".
> A while ago the AP made many small achromats (for guide scopes? ).
> I heard some responces about them. They are quite good. But this does
> not force Roland to claim that his achromats has "lack of colors" or
> that
> that made under "new formula" etc.
--------------------------------
Good for Roland...he was telling the truth. So is Stellarvue. Seems to
me the only one that has a problem with the truth is yourself. No?
-----------------------------------
>
> You need to know also, that SV does not produce their optics at all.
> Optics just selected from large batch made overseas in Far East.
-------------------------------------
Another lie. You know not that which you speak. The 80mm F6 lenses are
made TO STELLARVUE'S SPECIFICATIONS in the Far East. They are not the
generic Chinese achromat lens. In addition, the 102D's lenses are MADE
IN THE USA TO STELLARVUE's specification. Just how mis-informed are
you? See, you know nothing about what you're talking about! Does every
telescope maker actually manufacture their own lenses in house? NO!
They are manufactured by specialty glass companies to the telescope
maker's specifications. Duh! Do YOU manufacture each and every element
in the chromacor or do you have another company manufacture (and coat)
each lens element to your specifications. Your ignorance really shows
through on this one!
----------------------------------------
>
> Also, not the ARIES, not the AP was a discoverers of a new method
> of manufacturing of "well color corrected ACHROMATS" - an internal
> aperture stop! And why _internal_ ??? To hide this method from
> customers!
> Now, I believe, you have a clue who has a problems with color
> correction.
---------------------------
No, now I believe I have a clue as to who has a problem with telling
the truth.
David
>
>
>
>
>
> Finally. FYI, we already developed a small ( 10mm diameter!) Barlow
> lens 1.7x which will correct a false colors to insignificant level
> in such achromats like 70mm F/5-7 , 80mm F/5-7 and to very low level
> in
> 100mm F/5-7 .
> Lets hope, that SV scopes, according to your guess, has too
> different
> design from classical achromats and this lens will not work in their
> scopes. This will be much better for their potential competitors.
> (Apple vs Intel story).
>
>
>
> Valery Deryuzhin.
Sue_and_Alan_French
Yes, that was our 8" set up next to the AP folks.
Clear skies, Alan
"Isaac Newton" <ap...@gravity.com> wrote in message
news:3BBD15AC...@gravity.com...
> Details, details....I was busy inventing calculus.
> BTW - was that your 8" refractor set up by Roland at Astrofest?
Bill Becker
Hehehe...see what you started? ;^)
I know you know that good achromats have a place in the astro
community...you've said it before and I don't think you've changed your
mind since. The only problem you have is with the, sometimes, over
enthusiastic claims made by some in their joyful use of their scope. I'm
always pleased to see someone happy with their scope; almost guarantees
that scope is going to see a lot of use and that's what it's all about.
I have a Vixen 90mm f/11.1...actually 2 of them. My first one had a bit
of an accident; one night the wind blew too hard and knocked it over.
End result? The lens had a small crack near the edge and collimation was
thrown off quite a bit. Still, I tried viewing with it just to see what
the results would be. Turning the thing on a bright star(I forget
which), I found I could no longer focus it to a pinpoint and there was
alot of colour, more than I could remember seeing before the
accident.(that's the reason I picked up the second one, ota only)
I compared that view with a view through the new ota I had bought. Stars
were perfect pinpoints, there was a lot less colour and the diffraction
patterns on both sides of focus looked very close.
My point? If there are companies out there(like SV and D&G) who place QC
high on the priority list, the consumer is going to get a properly
collimated, respectable or better spherically corrected Achromat right
out of the box, which in mho, serves the public's needs.
Those that do purchase a SV achromat based on the claims being made...if
they find they are not satisfied they can always take advantage of SV's
liberal 30 day return policy. You'd think we would have seen some
unfavourable reviews of these achros by now but I know I haven't. Says a
lot I think.
Take care and clear skies to you,
Bill
ValeryD wrote:
>
> One of my american friend asked me to comment some statements
> he read somewhere in Yahoo news groups.
>
> He re-sent me a very interesting, to some degree typical, post.
> Here is a part of it:
>
> >>I will tell you that there is a Stellarvue 1010 owner who also owns
> a Vixen 102ED and TV Genesis who has stated that the 1010 performs
> nearly as well as the 102ED in terms of color aberration and that it
> can be pushed to nearly the same magnification before image breakdown
> and that's for a 80mm scope. I can also tell you that reports of the
> 102D from recent owners state that it achieves even better color
> correction than the 1010 and can easily be pushed to over 240x
> atmospheric conditions allowing. All achromats are not the same. I
> think anyone with an objective viewpoint would accept this. In any
> case I will let you all know how the 102D performs in a couple
> months. If you want to get a taste of it's performance right
> now,
> check out the Stellavue Yahoo group or Stellarvue's web site. Well
> worth it for anyone considering a 80mm to 102mm refractor.
> Regards.
> Tom.
> >>
>
> What I can say?
>
> 1. Vixen ED refractor glass combination allow to have 5x smaller
> secondary
> spectrum than the in a _best possible achromat_ of the same D and F/D
> .
>
> 2. Magnification pushing depends not only from color correction. It
> mainly
> depends from spherical aberration correction, optics smoothness and
> seeing conditions. So, the fact, that magnification in simple
> achromats
> can be pushed to 240x is not any kind of unique fact. In _any_
> achromat
> with well corrected spherical aberration and smooth optics and under
> good
> seeing conditions magnification can be pushed even higher - to about
> 400x
> (when observing double stars, for example).
>
> 3. False color perception greatly depends of used magnification and
> atmosphere transparency. As higher magnification, as lower surface
> brightness of a false color halo. At 2000x in 4" achromat one will not
> see any false colors on moon or even Jupiter.
> At foggy conditions violet-blue false colors will be also greatly
> reduced.
>
> 4. Some peoples, especially older persons, has greatly reduced eye
> sensitivity to a violet part of spectrum.
> Some peoples (mans 5x more often than womans) are colorblind in some
> degree.
> Both these factors can influence a color error estimation too.
>
> 5. Finally, some peoples simply don't like to see a false colors and
> make
> statements like above.
>
> The difference between Vixen achromat and ED APO is well seen in their
> prices. This price difference correctly reflects a differnce in color
> correction for both these scopes.
>
> It is simply impossible to create an achromatic objective of the same
> D
> and F/D which will stay even close to true (not fake) ED APO.
> Vixen's optical designers have the same (or better) access to
> different
> optical glasses as designer of these miracle achromats. They also not
> a bit less experience in optical desing science than 102D designer.
> However they are unable to create such achromat, that will approach
> a color correction performance achieved in ED APO.
>
> False myths have a unique property to survive in some sort of minds.
> This can't be argued at all. Above letter is a very good sample of
> this.
>
> Valery Deryuzhin.
> ARIES.
Stephen Tonkin
> Details, details....I was busy inventing calculus.
But, just like your telescope needed Hadley, your calculus needed
Leibniz to make it usable. And the less said about your corpuscular
theory and your dabbling in astrology the better!
Best,
Stephen
--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astronomy Books +
+ (N50.9108 W1.830) | <http://www.aegis1.demon.co.uk> +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
ValeryD
> Valery, your chromacorr, by virtue of it's 30mm clear aperature cuts at least
> 12-13mm into the light cone.
>
> How much chromatic aberration is reduced by this masking, and how much is
> reduced by the
> content of the glass?
>
> If the chromacorr changes the focal ratio from 150/1200 (f8) to 100/1200 (f12)
> the amount of colour
> will be equal to any other f12 achromat.
>
> Regards, Stephen Pitt
All these "cuts" were born in some companies which make these
notorious
new ED achromats. semi-apos etc.
Your brain is ill by SV. This is absolutely obvious. You
_intentionally_
try to discredit Chromacor stating that we do use a SV's approach to
color correction "improvement" - internal aperture stopping.
If you think that, I too, can use such approach, then, sorry, but you,
sir,
an idiot.
Valery Deryuzhin.
ValeryD
> "JMc" <tri...@mydeja.com> wrote in message news:3BBC8460...@mydeja.com...
>
> > There was a long thread some months ago about these scopes, and it seems
> > that some of the 80 mm f/6s, were actually 60 mm f/8s because of focus
> > tube vignetting. That may explain the better color correction that some
> > are claiming vs. the standard short tube offerings.
> >
> > Jim McSheehy
>
> guy who
> sells $750 light cone masks still masks on, incites and dupes the naive with
> endless
> tirades on mythology, and calls his competitions' pots black.
>
> Not too even-handed, I say.
>
> Best regards, Stephen Pitt
As complete idiot you constantly repeat the same false rumour that Chromacor
acts like aperture stop. The man, who think that others are idiots (me,
as a Chromacor designer and all users of Chromacors), is complete idiot
himself.
With last hope, that you still did't lost remnains of mind, let me
explain.
Chromacor clear diameter is 30mm
Back distance (from last surface)- 200mm
195:30 = 6.7
The cone is 1/6.7 This can't cause any vignetting in any Synta scopes
Chromacor was purposed for. All these scopes has cone 1/8 and slower.
Remember, if you can, that telling truth, a man can't become poor.
And the truth is - some SV scopes has an internal vignetting, not
Chromacor. Chromacor has enough fully illuminated field for small
CCD chips and its vignetting free circle is larger than in most
small MCT on todays market where a vignetting starts just from an
optical axe. Nobody weep about this.
Valery Deryuzhin.
Anders Hansson
respect your competence as an optical designer, but you are now calling
a highly skilled astrophotographer in this forum an "idiot". I find that
most objectionable.
Previously you wrote:
> We tested a Chromacor on
> some
> different achromats and the results were exactly according to our
> simulations.
> It was in the case with 70mm F/7 achromat as well as with 10" F/6.5
> and
> many between.
What brand was the 70mm f/7 ?
Anders H.
--
Correct address: anhn at telia dot com
ValeryD
> He used that colour correction technique until someone caught on to
> it.
> Then the apo hit the fan.
> -Rich
>
> On Thu, 04 Oct 2001 10:46:40 -0500, JMc <tri...@mydeja.com> wrote:
>
> >There was a long thread some months ago about these scopes, and it seems
> >that some of the 80 mm f/6s, were actually 60 mm f/8s because of focus
> >tube vignetting. That may explain the better color correction that some
> >are claiming vs. the standard short tube offerings.
> >
> >Jim McSheehy
Rich,
Bravo! Very true.
Valery Deryuzhin.
ValeryD
> No, now I believe I have a clue as to who has a problem with telling
> the truth.
>
> David
I am sure your knoweleges in scholastic is far far deeper than in
optics.
Finally, if a man can create his own speciafications for an objective,
he will for sure can eliminate a "mistake" with internal improper
baffles. But, as Rich A. correctly noted, they (read SV ) use this
color correction technique till this hidden fact was discovered.
May be YOU (as educated in optics?) was the person who tell SV to use
this technique? he he , you reasoning about truth!
You even don't know the difference with werbs "to use" and "to promote",
as N.Z. too.
Valery Deryuzhin.
ValeryD
>
> Other than being an obnoxious, why do you keep insisting on using the
> term "miracle achromats"? Would you like for everyone to start calling
> your chromacor a "miracle vignetting aperture mask"?
> I know that it isn't and that to call your chromacor this name would
> be incorrect. So why do you continue to make such an ass out of
> yourself?
>
> David
Dave,
You never saw a Chromacor and you don't know, that it was designed
to work WITHOUT vignetting with 1/6.7 cone, not say about 1/8
cone as in Synta scopes have. Chromacor has enough fully illuminated
FOV for small CCD cameras.
I see, that you, as like as Stephen Pitt, both have vignetting in
your minds and some SV scopes. ha ha ha.
Valery Deryuzhin.
Markus Ludes
Stephen,
Knowing details of chromacorr ? Knowing a bit math ?
Okay here we go:
Synta aperture 150 mm, focallenght 1200 mm
clear aperture Chromacorr 30 mm
space from Chromacorr lens to attaching thread of its housing : 65 mm
optimum spacing from chromacorr thread to focal point 161 mm
65 mm + 161 mm = 226 mm
1200 mm( focallenght) x 30 mm ( chromacorr apertur) : 150 mm ( aperture optik)
=
240 mm
This 240 mm is the maximum distance from focalpoint where the chromacorr
can be placest before it starts vigneting.
Can you do the rest math your self to find out how big is the 100% illuminated
field on the Synta 150/1200 under use of chromacorr or do you need help again ?
clear skies
Markus
>
> Valery, your chromacorr, by virtue of it's 30mm clear aperature cuts at least
> 12-13mm into the light cone.
>
> How much chromatic aberration is reduced by this masking, and how much is
> reduced by the
> content of the glass?
>
> If the chromacorr changes the focal ratio from 150/1200 (f8) to 100/1200 (f12)
> the amount of colour
> will be equal to any other f12 achromat.
>
> Regards, Stephen Pitt
>
>
>
>
> --
> Posted from ip-88-048.riv.pe.net [64.38.88.48]
> via Mailgate.ORG Server - http://www.Mailgate.ORG
--
Posted from pd4b888d6.dip.t-dialin.net [212.184.136.214]
Dave
Amazing, another distortion of the truth. Yes, the chromacor does not
vignett for ccd applications. Well, duh...ccd chips are very small. Of
course there is no vignetting for ccd applications. However, as you
stated on the stellarvue groups forum when specifically asked about
vignetting for visual use, you finally agreed that the chromacor DOES
CAUSE SOME APERTURE MASKING. From your own words above, you must be
exceeedingly poor.
David
ValeryD
> And you_intentionally target Stellarvue in each and every post to saa. I
> respect your competence as an optical designer, but you are now calling
> a highly skilled astrophotographer in this forum an "idiot". I find that
> most objectionable.
His skill in astro-photography (if it really high, in which I
personally
quite doubt) does not allow him to profatate a product he never saw.
And I am 300% sure he read all (or most) review of Chromacors and
didn't
missed the fact, that reviewers _specially_ noted, that on axis and
near
it a Chromacor is completely free of vignetting and don't have any
internal aperture stop. Than lie about Chr., he'd better tell this
(about internal stop) to SV chief.
> What brand was the 70mm f/7 ?
LOMO achromat. Vintage 1972. Excellent results - no colors at all
in or out of focus. Very close results we expect from our newly
developed color-corrector-barlow lens (CCBL) with 1.7x amplification.
This lens will be only 10-13mm diameter and will work more or less
good with any achromat in 60mm F/6 to 100mm F/7 range.
Valery Deryuzhin.
B.T.Marshall
I've been reading it hoping to learn something and I have learn a few things. But I
have learned nothing that would change my view about the value of the Stellarvue
scopes. At the very least all reports I have seen indicate they are very well made
achromats with excellent mechanics and are supported by excellent customer
service and a 30 day money back guarantee. I find it hard to believe anyone can
find fault with that.
In addition I have found nothing on the Stellarvue web-site suggesting
that these
are anything but well made achromats. It appears all you are complaining
about is
enthusiastic posts by users of these products and somehow suggesting
that implies
some sort of crazy marketing conspiracy executed by Vic Maris. This
discussion
has degenerated into absurdity and name-calling. Time to end this and
move on
to more productive discussions. In any case, I won't visit this thread
again. Regards.
Tom.
-- ____________________________________________________________________________ Benjamin Thomas Marshall GATS Inc. Voice (757) 873-5920 11864 Canon Blvd., Suite 101 Fax (757) 873-5924 Newport News, VA 23606
Rockett Crawford
Stephen Pitt wrote:
> > Doesn't anyone know of any "true myths" about achromats??
> >
> >
> > Rockett
> >
> > Capella's Obsservatory
> > http://www.jestercourt.com/~capella
>
> Hi, Rockett!
>
> It would be a "True Lie" if I did.
Agreed, but at least it wouldn't be redundant. ;^)
take care,
Rockett
Capella's Observatory
http://www.jestercourt.com/~capella
Mike Damato
I've read with interest this and earlier posts dealing with the whole
Stellarvue performance claims issue. I have a technical question about
it - and many of the people involved in this thread certainly have the
knowledge to shed light on this.
Question is, will inaccuracies in collimation or lens figure on
inexpensive achromats degrade the color correction? I ask because I
wonder if this whole controversy stems from users comparing the SV
scopes to the cheap short-tubes, not realizing that that many samples
of the cheaper ones do NOT perform at the theoretical limit of color
correction for achromats. In other words, its not that the SV's
magically exceed the 1/2000 limit, but that many of the Chinese
imports don't reach that limit. Could that be the source of the claims
of superior correction for the SV's? This, combined with the fact that
color error is relatively inoffensive at small apertures anyway, might
be the source of such claims.
Does that sound like a reasonable guess?
Thanks,
Mike
Brian Tung
> Amazing, another distortion of the truth. Yes, the chromacor does not
> vignett for ccd applications. Well, duh...ccd chips are very small. Of
> course there is no vignetting for ccd applications. However, as you
> stated on the stellarvue groups forum when specifically asked about
> vignetting for visual use, you finally agreed that the chromacor DOES
> CAUSE SOME APERTURE MASKING. From your own words above, you must be
> exceeedingly poor.
Regardless, if the center of field is unvignetted, then any color error
there is unmitigated. If the Chromacorr were really acting even
predominantly on aperture masking to do its work, it would be obvious
at center. I doubt that anyone would have missed that.
Stephen Pitt
news:5c4a4ee7.01100...@posting.google.com...
> > >
> > > Jim McSheehy
> >
> > Jim: Stellarvue corrected the problem immediately and publicly. However, the
> > guy who
> > sells $750 light cone masks still masks on, incites and dupes the naive with
> > endless
> > tirades on mythology, and calls his competitions' pots black.
> >
> > Not too even-handed, I say.
> >
> > Best regards, Stephen Pitt
>
> As complete idiot you constantly repeat the same false rumour
Val: False rumor? Out of your own orifice, you've said the same thing
I have written; that the chromacorr is an observation tool and ccd imaging
capable, and would vignette the photographic plane (43mm).
So, you claim the chromacorr will not cut into the light cone?
Yes or no, Valery. A simple answer will do for all the amateurs out there.
Regards, Stephen Pitt
that Chromacor
> acts like aperture stop. The man, who think that others are idiots (me,
>
> Valery Deryuzhin.
--
Posted from ip-88-114.riv.pe.net [64.38.88.114]
Stephen Pitt
> >
>
>
>
>
> --
Markus: I would be glad to test the chromacorr with my synta 150, which has a
very flat, evenly illuminated field at the film plane.
Early on, I used aperatures approaching 30mm very close to the advised
placement of the chromacorr, but observed severe vignetting at the film plane.
Only when I made the switch to a minimum 43mm size, did the vignetting go to
zero. That 43mm inside diameter is at the t-mount. Foward of that, nothing
less than 48mm exists.
You and Valery now tell me that installing the chromacorr in the same light
path will not vignette?
Show me.
Regards, Stephen Pitt
> Posted from pd4b888d6.dip.t-dialin.net [212.184.136.214]
> via Mailgate.ORG Server - http://www.Mailgate.ORG
--
Posted from ip-88-114.riv.pe.net [64.38.88.114]
Stephen Pitt
Hi Brian:
That the chromacorr cuts into the light cone is a fact Valery himself has
admitted several
times on other groups-that the device's application is limited to observational
and ccd use,
which uses only the sweet spot. My querry to him was and is: How much of the
corrective properties of the chromacorr are due to stoppage and how much is due
to material properties.
The irony, which is what my posts attempt to define is: Valery is the person
who waxes
near hysterically about light path constrictions in popular telescopes, yet
sells a device that
has a clear aperature of 30mm at a point where the cone of light is greater
than 40mm when
used in typical prime focus photography. Were I to employ the chromacorr
anywhere forward of the 43mm wide
film plane, there would be significant vignetting. The beginning
astrophotographer knows this.
I am all ears if it can be conclusively demonstrated there is no encroachment
of the cone
here.
Best regards,
Stephen Pitt
Chris1011
path will not vignette?>>
I think they mean that it will not vignet an on-axis beam, so you will get the
full 6" resolution when using it at high power for planetary viewing. For wide
field, yes, you are certainly correct, it would vignet in the corners of a 35mm
film plane.
Roland Christen
Al Hall
wrote:
>Even Vixen 102 F/6.5 has at least 5x better color correction (5x smaller
>secondary spectrum) than any 102mm F/6.9 achromat even if this achromat
>was designed by God. ^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^
It's been at least a few months since I've had to clean a mouthfull of
coffee off of my keyboard and screen while reading SAA.
Thanks Val!
Al
Al Hall
I agree. It's been months since you and Val have been drawn into a
protracted discussion of optics here in SAA. I've always found these
discussions to be illuminating and entertaining.
I remember you saying that you actually built a Chromacor like lens
for a refractor used by your club. I'm wondering if you've had a
chance to get your hands on one of Val's for testing or observing?
Al Hall
On 04 Oct 2001 20:33:38 GMT, chri...@aol.com (Chris1011) wrote:
>>>It is amazing that this keeps getting rehashed here>>
>
>Ah, but is this not more interesting than pyramids and numerology? There's
>actually some facts being presented, or maybe that's out of fashion these days?
>
>Roland Christen
Brian Tung
> That the chromacorr cuts into the light cone is a fact Valery himself
> has admitted several times on other groups-that the device's application
> is limited to observational and ccd use, which uses only the sweet spot.
> My querry to him was and is: How much of the corrective properties of
> the chromacorr are due to stoppage and how much is due to material
> properties.
I think I didn't convey my point clearly enough. Let me try again.
The "sweet spot" is fully illuminated; everyone appears to stipulate
to that. That means it bears the full brunt of any color errors
transmitted by the objective *and* the Chromacorr. If that sweet spot
reveals substantial color correction, that correction is due *solely*
to the optical properties of the Chromacorr, and not to an aperture
stop.
In other words, given that everyone agrees that the center of field is
unvignetted, aperture stopping can only affect color correction
off-axis; it cannot improve the color correction on-axis.
Mike Burley
My remarks interspersed:
"Ron B[ee]" wrote:
>
> It seem to me Mike that if Valery wants to market the Chromacor
> on the Stellarvue telescope, he can simply order one (or several)
> as he did with the 150mm Synta and 120mm Synta. Why should
> someone else be burdened with the expense of making the scope
> available free of charge (even for a limited time use) when the
> financial benefit will go to Aries. Finally, publish the result and
> market the Chromacor.
I suspect this may have been Vic Maris' rational as well. It's a point
well taken.
> Alternatively, as I've said many times in the past, Valery can
> also send a Chromacor to Ed Ting or Todd Gross whom I'm
> sure have access to so many scopes.
The Chromacors must be correctly matched with the scope used. Barry at
Orion (UK) "tested" a Chromacor on a optical test bench and made a hash
of it with incorrect spacing etc. He then posted a report that the
Chromacor didn't perform as advertised. I can understand Valery's desire
to exercise some control over independent testing.
<SNIP>
Mike in Oregon
Chris1011
I remember you saying that you actually built a Chromacor like lens
for a refractor used by your club.>>
Yes, it has a 3.5" aperture and is still working in the 10" club refractor.
Also, there is one in Los Angeles of the same design that was installed in an
amateur's 10" Zeiss refractor. He has now replaced the Zeiss lens with another
custom achromat and is still using the corrector - tells me he can't do without
it. A third one was made for a 6" scope, but I have lost track of it. The
design was written up in S&T back in the 1980's. The design can be scaled down
to be smaller and go further back in the scope. Big problem is getting this
glass made. Also, there is no way to know the quality of the glass ahead of
time, i.e. bubbles, striae etc. While I had good luck with the blanks I used,
another amateur recently told me that he received blanks with poor homogeneity
from Sovirel, so the project is now in limbo.
>>I'm wondering if you've had a
chance to get your hands on one of Val's for testing or observing?>>
No, I'm not on the waiting list.
Roland Christen
Stephen Pitt
>
> I think I didn't convey my point clearly enough.
Nor I, Brian, as I was not focusing on the sweet spot. In prime focus
photography
the entire field-ideally-is flat, evenly illuminated, and unaberrated. My
assertion is and has been:
Field vignetting due to cone cutting. In fact, the virtues of the chromacorr,
as it
applies to the remaining field size is-at least without a field test- without
argument.
Me thinks the horse is dead.
Stephen Pitt
news:20011005135208...@mb-cg.aol.com...
Leave it to a genuine lens maker to cut through the detritis. Thanks. Stephen
Pitt
Derek
optical expert and do not claim to understand a lot of the issues, but
wouldn't the simulation only be as good as the data being feed into the
model? In reading these posts it sounds like the initial simulations were
done without detailed information(glass being used, focal length). In this
case wouldn't the results just be a (good?) approximation?
Derek
chri...@aol.com (Chris1011) wrote in
<20011004163137...@mb-mv.aol.com>:
>>>
>Personally, I believe computer simulation is certainly a good start,
>but not an end all.>>
>
>Computer simulation is as good as it gets, far better than subjective
>"eyeball" guestimates. For instance, the computer simulation for a
>particular design says that at 430nm the color halo will be 150 microns,
>and by golly, when you actually run light through it and take an image
>at 430nm, you somehow get 150 microns.
>
>You have to understand that these programs were not developed by
>dummies, and that the whole science of optics has been peer reviewed for
>more than 150 years by people far more knowledgeable than myself or
>Valery or ...
>
>The whole giant optical industry all over the world is based on this
>science, and yes inddeee it does work, so unless you really know the ins
>and outs of optics, there is no point in making statements like:
>"computer simulation is certainly a good start, but not an end all".
>
>Roland Christen
Chris1011
What you are saying makes sense if all the variables are know. I am not an
optical expert >>
If you are not knowledgeable, would it not be prudent than to listen to the
experts? They have said that simulation does work. Why would you want to
question it without some knowledge of the facts?
Roland Christen
Rockett Crawford
Chris1011 wrote:
Car salesman are "experts" aren't they?
Rockett
> Roland Christen