Televue Or Takahashi???
Jim
enjoy this type of viewing. A quick lightweight altazimuth rig like a TV-102
on a Gibraltar mount would be nice rig for me.
I can see a high quality refractor in my future due a small windfall from my
employer. I think a scope like a 4" APO would make an excellent addition to
my scope collection.
An AP traveler is almost never available and is more than I want to spend
anyway. I am vacillating between a Takahashi FS102 or a Televue TV-102.
Which one would you choose and why.
Reef1969
TV101, or Genesis. It's a toss up for high power viewing.
Good Luck
Clear Skies
Richard
Jackie LaVaque
> An AP traveler is almost never available and is more than I want to spend
> anyway. I am vacillating between a Takahashi FS102 or a Televue TV-102.
> Which one would you choose and why.
Hmmm... well, neither of these will give you quite as wide a field of view
as your current scope, but I have used both myself and find them both to be
delightful telescopes. I have an FS102 myself, but almost bought a Tele Vue
102 just before I found the great deal on the Tak... I'd say to do an
"eenie-meenie-mynie-moh" if you want to choose the best one, because they're
*both* great!
Jackie
Pat Nealy
The Orion is an f6, the TV102 an f8.6. I'm not sure an alt az mount is
the way to go here. I have always considered the 102 more of a planetary
scope due to the higher focal ratio and the fact that there is less
glass in the path so theoretically, more contrast.
Used as a planetary instrument, a driven mount provides a far more
pleasant viewing experience.
I had a TV 102 and bought a Tak 102 to compare it to. I kept the Tak for
a month, and sold it to keep the TV.
As another poster mantioned, consider the TV f5.4 scopes
Genesis/SDF/101/NP101. These provide phenomenal wide field views and do
a decent job on the planets. Remember there are only three planets you
are going to see surface depail on, but thousands of widefield targets.
Pat
Ratboy99
>a decent job on the planets. Remember there are only three planets you
>are going to see surface depail on, but thousands of widefield targets.
>
An interesting point, but I would consider time spent at the eyepiece on each
type of object first. If all you do is stare at Jupiter all the time (which
some do), it doesn't matter how many other kinds of objects there are.
rat
~( );>
email: remove 'et' from .com(et) in above email address
EDWARD HILLYER
Brian Parker
lucky to
get one with good optics, the TV-102 has good optics in their first
year
of production which was 2 years ago since they have to advertise.
Right now,
the TV-102 has poorer optics because the advertisement are over and
they are
saving money. Now the Traveler, it has guaranteed minimum of 1/10 wave
optics
but to get it you have to wait for ages maybe into the next decade.
The Vixen
102 Flourite has no coatings in their flourite element making it
dimmer.
Therefore if one wants to be sure one would get a good 4" refractor,
just buy
it second hand from people who can guaranteed it to be at least 1/8
wave. But
then, if your interests is deep sky and would use the 4" scope at
below 100X.
Any of the above will do. It is only when one uses it for planetary at
above
150X that the wavefront error is important. Getting a 1/4 wave FS-102,
TV-102
is like owning a good 1/8 wave FS-78 in terms of their contrast
transfer at higher resolution.
Brian
"Jim" <mp3su...@wi.rr.com> wrote in message news:<7yFr9.96670$w63.1...@twister.rdc-kc.rr.com>...
Eric Fuller
Eric.
Rich N.
The TV-102 will easily mount on a Gibraltar mount. Its tube ring is
designed to be used on a Gibraltar.
The Tak FS-102 would require a special tube ring and maybe an
adapter.
Rich
Jim wrote in message <7yFr9.96670$w63.1...@twister.rdc-kc.rr.com>...
The Cat Guy
>type of object first. If all you do is stare at Jupiter all the time (which
>some do), it doesn't matter how many other kinds of objects there are.
The Ratmeister speaketh the truth. 98% of my observing time is on the sun. I
like faint DSO's, but I don't find them visually stunning to look at. They are
static. The sun, it's ever changin'! :)
Mark
The Catman
isob...@aol.com
www.geocities.com/mark_rosengarten
Jim Mueller
> Most new fs-102 are mostly of 1/4 wave optics, so you have to get
> lucky to
> get one with good optics,
If that's the case, then I might as well stay with my Synta refractor!!!
ed_witkowski
Snip
"the TV-102 has good optics in their first year of production which was 2
years ago since they have to advertise.
Right now, the TV-102 has poorer optics because the advertisement are over
and they are saving money."
Where did you come up with this one?
Televue makes high quality scopes.
Look on the first pages of S&T, looks like advertisements to me.
e w
Howard Lester
"The Cat Guy" wrote
> The Ratmeister speaketh the truth. 98% of my observing time is on the
sun. I
> like faint DSO's, but I don't find them visually stunning to look at.
That's because you've been staring at the sun too long!
Howard Lester
Ron B[ee]
size (especially with retractable dewshield resulting in looking a lot
shorter)), lighter weight (8.8lbs may work better on Gibralta than the Tak),
Questions? Just call Al or David Nagler.
Howver, as indubitable reality ;-) sets in, the Tak FS102 is current
one sale for $1895, a highway robbery price!
IMO, you won't be sorry with either.
Ron B[ee]
----------------
"Jim" <mp3su...@wi.rr.com> wrote in message
news:7yFr9.96670$w63.1...@twister.rdc-kc.rr.com...
Ron B[ee]
> the TV-102 has poorer optics because the advertisement are over and
> they are
> saving money.
This has not been my experience with my TV-102.
Ron B[ee]
Richard
wrote:
Looking at deepsky objects (faint ones) is quite interesting.
Mainly because they all show some detail, and the idea of actually
seeing something that is so far away is kind of awe-inspiring.
I had that feeling when I first saw 3C273 in a 15" reflector and
Stephan's Quintet in a 30."
-Rich
"If Blockbuster continues to offer only Pan & Scan versions of
major movies from Warner, or any other studio offering widescreen
and P&S, please consider NOT renting anything from them."
Tom T.
> lucky to
> get one with good optics, the TV-102 has good optics in their first
> year
> of production which was 2 years ago since they have to advertise.
> Right now,
> the TV-102 has poorer optics because the advertisement are over and
> they are
> saving money.
What in *interesting* theory...
How come I still see TV-102 ads?
Tom T.
William Mc Hale
: Most new fs-102 are mostly of 1/4 wave optics, so you have to get
Brian, would you care to document evidence for these statements? (Except
the lack of coatings on the flourite elesment of the VX102). All reviews
of both the Tak and the TV have been very good. Even the Vixen has
received very good reviews (and note the lack of coatings will only lead
to the loss of a few percent).
--
Bill
***************************************************************************
Eschew obfuscation.
---------------------------------------------------------------------------
Home page - http://www.gl.umbc.edu/~wmchal1
***************************************************************************
Joe Ringer
I think what he meant, make a great product to build a rep then cut cost and
drop your standards. If this is what he meant I think Shawn has a
challenger.
--
clear skies,
Joe
Tom Davis
"Joe Ringer" <jrin...@peabody.ringer.home> wrote in > I think what he
meant, make a great product to build a rep then cut cost and
> drop your standards. If this is what he meant I think Shawn has a
> challenger.
>
> --
> clear skies,
> Joe
>
> http://users.erols.com/jringer3/astro1.htm
I got that impression as well. Unfortunately, the poster
does not know how TeleVue does business. They have
not followed that philosophy at all. Instead, they work
at continually improving a product after introduction. My
second Genesis of the first series was better in every
way than my first. Better spherical correction, less color,
and a sliding dewcap, instead of a screw-on one. Each
successive model they produce gets improved with time,
not cheapened.
The problem with the philosphy in question is that it is
harder to build a reputation of quality than to lose it.
TeleVue is in business for the long haul, and recognizes
the need to keep their excellent reputation intact.
Thanks, Tom Davis
William Mc Hale
: Jim,
: The Orion is an f6, the TV102 an f8.6. I'm not sure an alt az mount is
: the way to go here. I have always considered the 102 more of a planetary
: scope due to the higher focal ratio and the fact that there is less
: glass in the path so theoretically, more contrast.
I wouldn't worry too much about the scope being limited to planetary work.
With a 35mm Panoptic the TV102 will provide a FOV of about 2.7 degrees,
that is plenty wide for most objects in the sky including biggies like the
Veil Nebula. Also of course contrast is good for deep sky as well.
: Used as a planetary instrument, a driven mount provides a far more
: pleasant viewing experience.
True, but it can be used in alta-az mode fairly readily until you get to
about 200X.
Jim Wayda
Would you choose the Tele Vue NP-101 over the TV-102? I believe that the
NP-101 is the best 4 inch Tele Vue scope.
-jim
"Ron B[ee]" <ro...@cox.net> wrote in message
news:3yXr9.170838$S32.11...@news2.west.cox.net...
William Mc Hale
: Ron,
: Would you choose the Tele Vue NP-101 over the TV-102? I believe that the
: NP-101 is the best 4 inch Tele Vue scope.
I agree the NP-101 is a great little scope. Unfortunately it does not
have a little price. I can certainly see someone choosing the TV-102 over
the 101.
--
Bill
***************************************************************************
A clear conscience is usually the sign of a bad memory.
Sean Golden
Brian shares a suspicious number of posting eccentricities with a
recently self-exiled troll we all know too well.
-sdg
Myriadimage
axis , 2.7" focuser and is the only 4" ED scope (OTA) under $1,200 that I know
of.
Joe Ogiba
Myriadimage
UWA 2" eyepieces in the 120 F5 and 14mm and up in the 150 F8. I use a 4" APO,
5" Mak or a 10" Dob for high power use.
Joe
Ron B[ee]
"Jim Wayda" <jwa...@cox.net> wrote in message
news:725s9.173438$S32.12...@news2.west.cox.net...
> Ron,
>
> Would you choose the Tele Vue NP-101 over the TV-102? I believe that the
> NP-101 is the best 4 inch Tele Vue scope.
>
> -jim
That's a very good question Jim, one in which
I've been asked several times and in which I
have thought about more than a few times ;-).
For me, I got a 4" APO primarily for viewing the
planets, moon, comet, you know the solar system
stuff. I wanted to get to 293x (on excellent nights
which is of course rare but still want to get to 220x
on more often nights) without a barlow. So the longer
focal length of the Tak and TV-102 (and the new
lighter tube TMB 100 f/8) seems a good match, not
to mentioned the price (at the time the TV-101 was
more expensive than both of these doublets). This
is not so say the the view of the f/8.6 TV-102 is
constricted, on the contrary it still gives me a whopping
3d FOV! This is also by no means implied that the
view through the NP-101 with a Powermate is bad,
I have heard only good comments from owners who use
Powermate with it. Just my personal perference. Although,
I've done lots of DSO viewing with my Light Cup (now over
200 non-Messier objects!), I still love watching the planets
whenever I could (especially Mars and Jupiter). After long
and meditative thoughts, I *personally* would still go with
the "less than perfect" :-( TV-102, but indeed a "perfect"
alternative to the economically deprived ;-). I'm glad Tele
Vue made these choices possible (in the same vein as
the Tak FS102/106FSQ ;-).
Ron B[ee]
PS But the highway robbery price of the Tak FS102
threw us all a "curved ball" ;-) and if I were deciding
on a 4" APO today ... ;-).
Tom T.
Agreed...
Tom T.
Tom T.
>
> Would you choose the Tele Vue NP-101 over the TV-102? I believe that the
> NP-101 is the best 4 inch Tele Vue scope.
>
> -jim
>
>
Some folks still feel there are reasons to choose the 102 over the
101. Obviously, for the simple fact is there would be no more 102's
if Al didn't sell them. I do have my own reasons (and believe it or
not, price actually had little to do with it) but then again, you
weren't asking me.
Tom T.
Steve D. White
wrote:
>Most new fs-102 are mostly of 1/4 wave optics, so you have to get
>lucky to
>get one with good optics, the TV-102 has good optics in their first
>year
>of production which was 2 years ago since they have to advertise.
>Right now,
>the TV-102 has poorer optics because the advertisement are over and
>they are
>saving money.
<snip>
>Brian
Brian;
Your information is totally incorrect. Where did you get this idea??
1) The fact is that we haven't changed one thing about the telescope
optics or manufacture since the introduction.
2) You should open up any issue of S&T since the TV102 was
introduced, including the latest, and he'd see that we have been
continually advertising the it.
3) You should also note that if there is ever a question about the
quality of a Tele Vue telescope, the owner should call us at (845)
469-4551 to discuss it. Any scope needing work, either repair or
warranty, can be sent back to the factory in NY that made it.
Steve D. White
TeleVue USA Rep.
swh...@got.net
Ratboy99
>Your information is totally incorrect. Where did you get this idea??
Umm, maybe from Shawn?
rat
~( );>
email: remove 'et' from .com(et) in above email address
EDWARD HILLYER
Alan French
That has absolutely nothing to do with the current discussion, and bringing
it up makes you look pretty petty.
Clear skies, Alan
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:5EIs9.107$Lt.6...@news.uswest.net...
Tom Papa
wrote on 10/20/02 3:44 PM:
I have a TV101. Color is perfect, which is to say non existent on the limb
of the full moon, Jupiter or Vega. Edge to edge the optics are sharp. With a
2X Posermate at F/10.8 the 101 has been the equal of a FS102. The contrast,
sharpness and clarity are unsurpassed. The TV101 has been much more
favorably commented upn than 8" SCT's, 5" Loma Maks, and a host of other
scopes by the owners of the other scopes. DSO's are dim and fuzzy in the 101
just as they are dim and fuzzy in most other scopes up to 8"'s. The larger
apetures are fine. They have a place in anyone's list of scopes to own. I am
very impressed with what can be seen and enjoyed in a very fine apo.
My $.02
tom
EDWARD HILLYER
when I told this group in August-Septemeber Lumicon WAS closing?
Can we trust whatever Steve tells us?
"Tom Papa" <tgp...@mac.com> wrote in message
news:BA33FAA2.5A6%tgp...@mac.com...
Craig Levine
> Is this the same Steve White that vehemently denied Lumicon was closing,
> when I told this group in August-Septemeber Lumicon WAS closing?
> Can we trust whatever Steve tells us?
>
>
Look troll,
If you have a personal beef with Steve, take it off-line mano-a-mano.
Could it have been that perhaps (note: speculation) Lumicom may have
give TV every assurance that things were fine, then *poof* gone. I've
had this happen to me at least three times in my business life. You
trust those who you are dealing with when they say things are fine, no
worries, our house is in order etc, despite rumours to the contrary.
Then they disappear. Maybe Steve was going on the belief that a
long-time TV dealer was fine, because they told him so. Keep in mind
Lumicon had been in business for over two decades.
Be careful who you slander and where - online speech follows the same
rules as off-line.
Craig
Craig Levine
Secretary
RASC, Halifax Centre
www.rasc.halifax.ca
Etok
close choice between the Televue and the Tak FS-102. They were my picks when
deciding on a 4" APO.
Either scope will provide absolutely delightful views.
My decision to go with a Tak was based on price and some favorable
comparisons I read on a particular website that reviews telescopes.
Would I trade it for a Tele Vue? No, well, maybe for the NP 101. Maybe.
But I must admit, the Takahashi FS-102 is superb, and every bit as good as
the tele-vue for a few hundred dollars less (speaking about the TV 102, of
course).
In my opinion, whichever choice you make, you won't regret it. They're
different, but optically, it's a pretty close match. I bet if you covered
the scopes up and just let someone peer through the EP's, there are very few
observers who could tell the difference--well the tak is an F8, so that
might give a clue.
"Tom Papa" <tgp...@mac.com> wrote in message
news:BA33FAA2.5A6%tgp...@mac.com...
______________________________________________________________________
Posted Via Uncensored-News.Com - Still Only $9.95 - http://www.uncensored-news.com
<><><><><><><> The Worlds Uncensored News Source <><><><><><><><>
Ratboy99
>comparisons I read on a particular website that reviews telescopes.
Mine was based on aperture. I wish that Televue would make some bigger apos.
mark d. doiron
news:20021229181109...@mb-ft.aol.com...
> I wish that Televue would make some bigger apos.
Rat--
i seemed to recall that one of the 140s was up for sale last year. now,
*that* would be sweet! but, it would be real nice to see TV jump into
the 5" apo market.
clear, dark skies--
mark d.
EDWARD HILLYER
Taks 102 vs Televue 102-102.
His results confirm my own tests: TV apos are 1/4 wave barely, at the film
plane.
Taks 102 are 1/4 to 1/8 wave , so Taks are consistently superior in good
seeing.
And I would not trust Steve White , after his fiasco with the disinformation
he gave before on Lumicon too in the past.
Alan French
We can probably assume that at some time you were wrong about something.
Can we therefore conclude that you are not trustworthy? But I guess you'll
run this flag up the pole whenever Steve writes something you disagree with.
Clear skies, Alan
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:BKwP9.397$B65.1...@news.uswest.net...
David Low
> Its' a fact that Mike Palermiti, optician with $150k equipment, has tested
> Taks 102 vs Televue 102-102.
> His results confirm my own tests: TV apos are 1/4 wave barely, at the film
> plane.
Where are these results (and the experimental methods) published? Are you
talking about spherical aberration?
Thanks,
David Low
EDWARD HILLYER
He was talking about the overall correction at the focal plane.
"David Low" <davi...@acm.org> wrote in message
news:g3iQ9.375289$pN3.42600@sccrnsc03...
Chris1011
tested> > Taks 102 vs Televue 102-102.
> > His results confirm my own tests: TV apos are 1/4 wave barely, at the
film> > plane.>>
Unless he has a green light interferometer, he cannot make those assertions.
Without a true interferometer, he cannot say one way or another what wavefront
accuracy the scope has, no matter how calibrated his eyeball is. He is also
associated with a competitor, so he is not exactly an independent investigator.
Roland Christen
ValeryD
And one more important point. 1/4 wave says nothing about telescope
real quality. It is possible, that a local point has such an error,
but the rest objective surface has excellent quality. The only RMS
wave front give us enough information about optics quality. Of course,
as Roland specially underlined, the test must be done in a green (or
yellow) light. Not in red light.
And, finally, the cost of testing equipment prove nothing.
Vaalery Deryuzhin.
EDWARD HILLYER
mr spindlelegs
photographic results if you do astrophotography) give you the most
important information. I don't mean just the star test when I refer
to what your eyes tell you.
Also, only a moron would pay $12,000 for a 5" APO. Zeiss may have
been the best but any marginal improvement they have over the
competition doesn't warrent that kind of money.
Nuff said.
Dave Keller
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message news:<J2OQ9.51$7I5.1...@news.uswest.net>...
> --
mark d. doiron
news:J2OQ9.51$7I5.1...@news.uswest.net...
> Why do you guys at AP, TELEVUE , APM USA,
> expect your buyers to IN FAITH accept something
> that YOU advertise as such and such in quality, and
> charge $$$$thousands?
Edward--
i bought a TV-ren-101. i don't think that the test report you propose
would have affected my decision to buy it. in fact, my buying decision
was driven a lot by reports from satisfied users that it was a quality
product. that, for me, was infinitely more important than a test report
that would become fodder for pointless arguments on saa. it was also
more important than mfg's claims, since those are, as you suggest,
subject to hyperbole (though this remark should in no way be interpreted
to mean that i agree with your own remarks about the quality of certain
mfg's).
a data point: i also own a Starmaster with a Zambuto mirror. that did
come with a test report (on the primary only). while it's an
interesting piece of paper, i am also quite confident that the fact that
i received it also didn't matter a bit in the decision to buy that scope
(i didn't even know i would receive it until i picked up the scope 6
months after ordering it).
i can't possibly speak for everyone, but i'd be really surprised if very
many folks wanted the type of test report you propose. i think that
what matters to most scope owners is performance under the sky (and yes,
more than just a star test). that type of respect must be earned from
users/owners of the scopes.
Chris1011
owners consistently knew what they were getting. And I don't care who =
you ask, the best experts in the Optical Fabrication Industry will still =
tell you NO ONE ELSE can achieve what Zeiss has done with their APQ =
apos.>>
That's not exactly true. While the quality of Zeiss lenses was very high, a lot
of modern Apos are of similar quality, and in some cases of higher quality.
Zeiss did provide interferograms made in red light with their APQs. These test
reports are meaningless. Would you like to refute this statement?
The fact that you and others were fooled into thinking that these red light
interferograms were useful does prove to me that test reports per se, are
worthless and are simply marketing tools. A lot of amateurs simply have no idea
how to interpret them, and marketeers can take advantage of that fact.
Roland Christen
David Low
> Zeiss did provide interferograms made in red light with their APQs. These
test
> reports are meaningless. Would you like to refute this statement?
Well, I certainly can't refute it, but I'm curious to know why it's true.
My uninformed intuitions tell me that, while a green laser interferometer
would be preferable, a red one should not yield appreciably different
results (e.g. in terms of Strehl ratio).
And as much as I am annoyed by Mr. Hillyer's passion for capitalization, I
agree that some metric of telescope quality would be desirable. It would be
nice if there were some industry uniformity, but failing that, knowing the
test method and results is better than faith in vague marketing assurances.
David Low
David Low
> Also, only a moron would pay $12,000 for a 5" APO. Zeiss may have
> been the best but any marginal improvement they have over the
> competition doesn't warrent that kind of money.
Economics for collectors is driven by supply/demand rather than utility.
When selling price is higher than purchase price, ownership can be a
rewarding experience.
David Low
Chris1011
Well, I certainly can't refute it, but I'm curious to know why it's true.
My uninformed intuitions tell me that, while a green laser interferometer
would be preferable, a red one should not yield appreciably different
results (e.g. in terms of Strehl ratio).>>
Your intuition is correct if you would measure only pure mirror systems, but
here he is referring to refractive systems. Would you believe that even SCTs,
which employ a refractive element, would be only 1/4 wave P-V in the green if
the red light interferometer said that it was 1/100 wave P-V? Since we do most
of our visual work in the yellow-green part of the spectrum, vs. the red (where
your eye sensitivity drops to less than 2% at night), would it not make sense
to measure the optic in green light? For further information on how refractive
systems work, a good book on the subject is Rutten & vanVenroiij - Telescope
optics, testing and evaluation.
>>And as much as I am annoyed by Mr. Hillyer's passion for capitalization,
Iagree that some metric of telescope quality would be desirable. It would
benice if there were some industry uniformity, but failing that, knowing the
test method and results is better than faith in vague marketing assurances.
David Low
>>
I can't speak for others, but in the case of our company, Astro-Physics, I have
covered this with our customers and on the apug many times. For your
information, I have posted interferograms showing best and worst performance of
a typical production run at:
http://groups.yahoo.com/group/ap-ug/files/130F6%20test%20reports/
I guarantee that all lenses will fall somewhere in between. If that is too
vague, then I can't do any more for ya.
Roland Christen
David Low
> Would you believe that even SCTs,
> which employ a refractive element, would be
> only 1/4 wave P-V in the green if
> the red light interferometer said that it was 1/100 wave P-V?
I admit this would only make sense to me if there were nonlinear optical
interactions (crystalline lattice, uniformly sized occlusions, etc.), but in
this case a green laser interferogram might show excellence whilst blue or
red was being cast to the winds.
> I guarantee that all lenses will fall somewhere in between. If that is too
> vague, then I can't do any more for ya.
I feel AP has done enough. I have an AP 130 F6. I am pleased with the
instrument and satisfied by published data and assurances of quality
criteria. This is partly because AP has demonstrated an unusual business
ethic, and in doing so has established a trust relationship with its
customers.
Televue and Takahashi have little or no published data, vague assurances of
quality, traditional commercial ethics, and only an anecdotal basis for
trust. They may make fine instruments but I'd like to see some data,
please.
David Low
Chris1011
> which employ a refractive element, would be
> only 1/4 wave P-V in the green if
> the red light interferometer said that it was 1/100 wave P-V?
I admit this would only make sense to me if there were nonlinear optical
interactions (crystalline lattice, uniformly sized occlusions, etc.), but in
this case a green laser interferogram might show excellence whilst blue or
red was being cast to the winds.>>
The real cause for the discrepancy is that most (not all) refractive optics
exibit some amount of spherochromatism. For refractors such as the APQ, if the
red is dead nuts perfect, the green will be overcorrected, and the blue even
more. Therefore, a red light interferogram is pretty much meaningless.
Roland Christen
Brian Tung
> > Would you believe that even SCTs,
> > which employ a refractive element, would be
> > only 1/4 wave P-V in the green if
> > the red light interferometer said that it was 1/100 wave P-V?
>
> I admit this would only make sense to me if there were nonlinear optical
> interactions (crystalline lattice, uniformly sized occlusions, etc.), but in
> this case a green laser interferogram might show excellence whilst blue or
> red was being cast to the winds.
Why wouldn't dispersion be enough to do the trick? Differing indices
of refraction mean differing light paths, and possibly sizeable changes
in the magnitudes of aberrations. Spherochromatism--the variation of
spherical aberration depending on color--is an example of this.
Brian Tung <br...@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
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David Low
> Why wouldn't dispersion be enough to do the trick? Differing indices
> of refraction mean differing light paths, and possibly sizeable changes
> in the magnitudes of aberrations. Spherochromatism--the variation of
> spherical aberration depending on color--is an example of this.
Thanks, Brian. I've found that the fastest way to learn is to start off
completely wrong. This is an approach I follow frequently.
David Low
Rod B.
<snip>
>Televue and Takahashi have little or no published data, vague assurances of
>quality, traditional commercial ethics, and only an anecdotal basis for
>trust. They may make fine instruments but I'd like to see some data,
>please.
>
>David Low
As an engineer, I must admit that plunking down what is a non-trivial hunk
of money for a 102mm version of one of these manufacturer's instruments, and
having to wait for my first views to confirm its performance felt real
uncomfortable. I think that at this level of investment any company
delivering a product consistent with its 'implied' quality should have no
issue with guaranteeing some 'minimum' level of optical quality. Unless that
minimum level is so low that the implied quality of the company would suffer
(with the resulting loss of sales), I can see no reason why it would not be
done.
Rod
me
best&worst
performance and guaranteeing that units fall within this range. Test
results for each unit are unnecessary for production scopes, IMHO.
If you still want your interferogram, you pay extra for it! Some optical
vendors provide this as an option.
NH-Rob
"Chris1011" <chri...@aol.com> wrote in message
news:20030102110220...@mb-cu.aol.com...
Markus Ludes
-V?
The real cause for the discrepancy is that most (not all) refractive
optics
exibit some amount of spherochromatism. For refractors such as the APQ,
if the
red is dead nuts perfect, the green will be overcorrected, and the blue
even
more. Therefore, a red light interferogram is pretty much meaningless.
Roland Christen
-------------------------
Roland,
happy new Year.
What you say above is correct, but there are other things to consider
as well. Our 80 mm TMB maker nulled the lenses for green , but shipped
with first run a red testreport. Retesting showed they have been
really nulled for green and the green report showed a bit better
numbers.
Due our pressure, he supply now green reports.
A Manufactor knows his design and if he knows it, a red testing will
give him enough info to be able to say, yes we reached the quality,
since he is using for nulling not only the interferometer.
In another case , a red or a green report can tell you only the
half storry, sample:
A Apo have more or less spherochromatism. In case of more , a good
green report does not say, the lens is very good, because the red
or blue could be more than half less quality.
So my question: Is a lens with green quality 1/8 wavefront, and red
and blue quality
of 1/3 or max 1/4 wavefront called a good lens ? maybe, but for shure
not called
a very good lens. But this lens show in green maybe 98% strehl, so
everybody think he have an very good lens, where he really have only a
so so lens
If spherochromatism is very very good controlled in a design, the
testnumbers
will not differ very much between green and blue or green and red
So without knowing the design and manufactoring controll on glas and
curvatives etc. , a testreport can give you a false impression about the
quality you think you getting
is above correct ?
clear skies
Markus
--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
Max The WooWoo
> telescopes, PLEASE INCLUDE a simplified Optical Test Report, like ZEISS
> has done for years with their scopes.
Why, oh why do I get this image of a pair of the worst sort of people
in our hobby standing around at Star Party, waving pieces of paper
with graphs and lines at each other, argueing about whose scope is
best due to what graph and line, and never actually using their
telescopes to look at anything?
Max "Let's have a Dob-waving contest instead!"
David Low
> Why, oh why do I get this image ...
I dunno. Perhaps because you've forgotten your medication?
David Low
Jan Owen
"Max The WooWoo" <maxw...@hotmail.com> wrote in message
news:537dd4db.03010...@posting.google.com...
> "EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:<J2OQ9.51$7I5.1...@news.uswest.net>...
SNIP!
>
> Why, oh why do I get this image of a pair of the worst sort of people
> in our hobby standing around at Star Party, waving pieces of paper
> with graphs and lines at each other, argueing about whose scope is
> best due to what graph and line, and never actually using their
> telescopes to look at anything?
SNIP!
Because you have surmised precisely that this is not only EXACTLY what will
happen; it actually already HAS happened. And more than one exceptional
telescope has been returned to more than one manufacturer, not because it
was a poor performer, but because it's supplied interferometry documentation
indicated it's RMS or Strehl NUMBERS weren't quite as "good" as someone
else's!!!
Rod B.
but rather that a minimum out-of-the-door specification be published for all
products within a line. With this system a company sets the standard it
wants to meet for the market it supplies, and the customer is guaranteed
that his investment is backed by a published minimum specification. As in
all manufacturing processes, the method of verifying the claimed precision
is key to specifications being worth anything. But then, any ethical company
isn't going to try to cloak it's specification in some misleading test
procedure. Based on the historical quality of the two manufacturers
mentioned earlier, it is obvious that their integrity and commitment to
quality meets the market expectations, but business is business, and I'm
quite sure they don't rely on verbal assurances from their providers. To
expect that their customers should accept less than they demand seems
curious.
Rod B.
Max The WooWoo wrote in message
<537dd4db.03010...@posting.google.com>...
rande...@aol.com
> I think what AP does is more than adequate ... providing test results for
>best&worst
>performance and guaranteeing that units fall within this range. Test
>results for each unit are unnecessary for production scopes, IMHO.
Since their production is low, since they say they test at each step,
since the scopes cost alot of money, why couldn't they provide
test results for all of them?
-Rich
David Low
> And more than one exceptional
> telescope has been returned to more than one manufacturer, not because it
> was a poor performer, but because it's supplied interferometry
documentation
> indicated it's RMS or Strehl NUMBERS weren't quite as "good" as someone
> else's!!!
So Jan, you're saying: "There are some idiots out there who misuse
information. Therefore, to be on the safe side, we should all be treated
like idiots who might potentially misuse information."
David Low
Jan Owen
My position remains unchanged.
"David Low" <davi...@acm.org> wrote in message
news:zZtR9.433125$GR5.1...@rwcrnsc51.ops.asp.att.net...
Alan French
When companies have provided actual results, they get calls from people who
want to know why their lens doesn't have the better numbers their friends
has. The also get returns from people who aren't quite happy with the
numbers they got. People don't seem to understand that there is a point
where the differences are completely meaningless in terms of actual
performance - they want the paper and the bragging rights that go with it.
I can well imagine companies do not want to waste their time with such
things. I see no problem with a guarantee that a particular optic is better
than some specific criteria.
Clear skies, Alan
<rande...@aol.com> wrote in message
news:qvmc1vod934l0agal...@4ax.com...
EDWARD HILLYER
up if the optics are still barely adequate, and let them thru for sale.
Televue's lenses are the worst in this regards. I have seen not 1 but 2
samples of the TV101 and the TV85 show 1/4 wave in green at the film plane,
and also 1/3 wave in 2 out of 4!!!! They get the lenses from Taiwan , and
the scope is ONLY assembled here in the USA.
"Alan French" <adfrenchre...@nycap.rr.com> wrote in message
news:64CR9.73368$eq2.18...@twister.nyroc.rr.com...
Enyo
dynamometer report on the engine as well as all the individual
specifications and testing results on all components and assemblies. If one
is a professional then one might pay the price for a few of these things but
not at a consumer level.
Alan French
Please provide the data that backs up your claim. How were these lenses
tested, and where are the results available?
What's this "at the film plane" all about?
Clear skies, Alan
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:HtDR9.12$1l1....@news.uswest.net...
mr spindlelegs
Your original post discussed the issue of high-end, multi-thousand
dollar telescopes not coming with certificates that show how good they
are. Do you apply this rationale to all multi-thousand dollar items
purchased in real life?
For example,
1. Do you demand that the car you purchase comes with a certificate
itemizing every measured tolerance in the vehicle? Did they get all
the clearances right? Did they tighten every nut and bolt to within
designed torque parameters? Did they perform the fuel efficiency test
on every unit as it came off the assembly line, regardless of how
unrealistic the EPA fuel efficiency test is? Or do you just look up
key pieces of data such as general fuel economy, appearance,
drivetrain combination, insurance costs, sales price, etc., then take
the vehicle for a test drive in order to determine if it satisfied
your needs?
2. High-end TV sets also qualify as multi-thousand dollar purchases.
Did you break out a magnifying glass and count the number of
horizontal lines to verify the manufacturer's claim on tube
resolution? If the manufacturer claims a certain wattage output from
the internal sound system, did you measure to see that it meets this
claim? Did you ask for a Certificate of Analysis with the TV set?
3. Houses definitely qualify as multi-thousand dollar purchases and
apartment rentals also are relevant. Did you break-out the tape
measure to verify the square footage claim? Did you run a thermal
efficiency test on the water heater to validate the claim on the
sticker or did you just pay the hot water bill and set the thermostat
to where it is not too hot, not too cold but just right? Did you run
the same efficiency tests on the oven, refrigerator, and
air-conditioning systems (if they came with the purchase/rental). If
they did not come with the purchase/rental, did you validate the
marketing claims on the units you had to buy to furnish these
properties?
If you are going to get on your soapbox about certifications, make
sure you apply it across the board.
The reason nearly all products purchased in life have no certification
reports is that it adds too much overhead in paperwork and additional
employees to handle the paper and man the phones to deal with customer
complaints. There are definitely other factors that will increase
overhead but the two I've just named are sufficient. Thomas Back/TMB
Optical has already pointed out the customer complaint issue in detail
which supports my argument.
Concerning your claims below about seeing 1/4 wave and 1/3 wave
performance in green at the film plane, post the specific serial
numbers on these scopes, who originally bought them and where, who did
the green light testing (must post actual test documentation and name
the testing sources). How do we know that the measurements you claim
aren't the result of independent tester screwing-up?
Dave Keller
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message news:<HtDR9.12$1l1....@news.uswest.net>...
Rod B.
The difference is that in every one of your examples, the manufacturer
publishes the essential specifications of the product. There is a published
figure for one to use as a basis for purchase, and for resolving issues with
quality or performance. The issue that started this thread, is that some
high-end optical instrument manufacturers do not publish specifications, and
even when requested, it's not forthcoming. I suppose the real issue is, to
what level of performance are they responsible. People with differing levels
of experience will anticipate differing levels of performance, but how does
an experienced, trained observer willing to plunk down the bucks, know with
certainty that his scope will meet his level of expectation. And as
importantly, if they are is displeased, to what precision can he expect
resolution with no published guarantee of performance? It's simply not how
business is conducted. Doing what AP does is the answer, only I see no need
to specify the high end, the low-end specification sets the quality bar. It
eliminates the 'his is better than mine' argument, that people are so eager
to point out.
Clear skies,
Rod
mr spindlelegs wrote in message ...
mark d. doiron
news:HtDR9.12$1l1....@news.uswest.net...
> I have seen not 1 but 2 samples of the TV101
> and the TV85 show 1/4 wave in green at the
> film plane, and also 1/3 wave in 2 out of 4!!!!
Edward--
that's a pretty outlandish claim, which, in and of itself, doesn't make
it false. however, it's so suspect that it should be held to the same
high standard that you demand of the mfg's of fine scopes: you should
at least provide relevant details--scope serial numbers, testers, TV
reaction, full test reports, etc. i'd be most interested in how it was
ascertained that the problem wasn't in the test
apparatus/procedure/testor rather than in the scopes.
EDWARD HILLYER
Guide and Consumer Reports!!
"Enyo" <En...@bigfoot.com> wrote in message
news:_qER9.94661$hK4.7...@bgtnsc05-news.ops.worldnet.att.net...
Rod B.
product specifications. I make no claim of poor performance by any
manufacturer mentioned in this thread. My observations deal strictly with
the issue of publishing product specifications.
Regarding specifications, I have noticed that almost all of the high-end
manufacturers of diagonals publish a flatness specification. Anyone know of
any issues caused by that?
Rod B.
Rod B. wrote in message ...
Alan French
Diagonals are sometimes priced according to flatness, and I believe at least
one company sometimes has a few that are much better than average and prices
them accordingly. I suspect this approach probably keeps the "fussy" crowd
happy, and they have an optic they can brag about.
I've also noticed that some companies will hand select a "premium" mirror
from those on hand for an extra charge. I wonder what happens if you have
six mirrors and six customers paying the "premium." Each could get the best
"on hand." All in all optics can be a very odd business.
Snowy skiee, Alan
"Rod B." <blue...@nospamworldnet.att.net> wrote in message
news:xbMR9.95349$hK4.7...@bgtnsc05-news.ops.worldnet.att.net...
> [SNIP]
Max The WooWoo
> Max The WooWoo wonders:
>
> > Why, oh why do I get this image ...
>
> I dunno. Perhaps because you've forgotten your medication?
No way dude, I know a glue fume hallucination when I see one.
Max "Or is it the chinese packing grease?"