LETTER TO AP+TAK+TELEVUE+TOM BACK (TMB)
EDWARD HILLYER
Cover2Cover
... this ought to be good!
- Don
EDWARD HILLYER wrote:
> To ASTRO-PHYSICS, TELEVUE , TAKAHASHI and TMB USA (Thomas Back)
> Manufacturers: The time has come for you to show with solid facts
> what it is that your customers pay for. You expect us to pay thousands
> of dollars for one of your Telescopes and tell us simply its
> "diffraction limited " in Televue case, or "1/10 wave lenses" in the
> case of AP? Until YOU supply an Interferometry Test Report with each
> scope you sell, you expect consumers to be pulled by the ear around a
> circle and believe IN FAITH in your advertisements ? Words are cheap.
> Lab Test Reports are what you SHOULD provide. (Star tests DO NOT tell
> the whole story.)In fact , it would be economical for you in the long
> run, and profitable, if you REALLY are selling/making optics to the
> level you promise, to provide proof with each scope.ZEISS had it right
> when it gave EACH Maksutov and APQ apo new owner a Test Report. Those
> scopes are STILL the most expensive on the market , even after the
> Amateur Telescopes section closed in late 1995.No one can match what
> Zeiss did optically, and you know it!But at least give your buyers a
> Test Report from Interferometry, and don't tell me "but then each
> owner would claim<< my scope is better than his/hers, theirs, >>etc"
> No excuses please.It's time the whole truth comes out. When I worked
> at Lumicon I HAVE SEEN on our neighbors Zygo (he's making optics for
> the military) a TV-101 BARELY being diffraction limited. Seen a TAK
> FS102 a little better than that, another FS102 really good, an older
> AP 6" exactly at the diffraction limited performance , but no 1/10
> wave at the film plane, no sir.And don't tell me I don't know what I'm
> talking about. I spent the last several years researching this issue
> and testing your claims.Start delivering what you promise by supplying
Bill Becker
wave overall and mine only comes out at 1/9th wave. What's up with that????
I'm sure that for the majority of us, we couldn't tell the difference if it
could save our soul. 1/6th, 1/8th, 1/10th, 1/12th wave,.....it's all good.
If the in focus image
gives me what I'm expecting from a scope.....I'm happy.
Best regards,
Bill
Jan Owen
I think the vast majority of folks who buy these scopes know in advance what
they are getting, and their makers put their names behind the promise of
quality. Buyers are not disappointed.
There is a lot of pissing and moaning on this group about a lot of things,
but we don't really hear about these scopes being poor examples of the
telescope makers' art. To the contrary. These are among the best scopes
available to amateurs. As for price, these scopes are simply a good example
of supply and demand at work. They cost is consistent with what folks are
willing to pay for what they perceive they will get, or what they already
know they will get based on prior experience.
Those who cry the loudest that they want interferometry with their scopes
almost invariably want it, not as a guarantee of quality, or as direct
evidence of quality, but purely for bragging rights. And we have already
seen that when one of these ego-trippers gets a scope with an interferogram
less than their buddy, the first thing they want to do is sent it back in
order to get one with a BETTER interferogram than their buddy.
The real proof of telescope quality to it's owner, is at the eyepiece, not
on a piece of paper. That paper means squat under the stars. The majority
of observers wouldn't be able to distinguish between a 1/5 wave optic and a
1/10 wave one visually, so tell me what the interferogram really buys you.
Squat. But it IS a meaningful system for testing an optic during
manufacturing to ensure consistent quality.
So I'd advise you to either buy one of these scopes and see for yourself, or
buy a 14.5" Starmaster with Zambuto mirror, which in terms of pure
performance, will kick all their butts on most objects under most
conditions, and go away and have a ball!
All this pissing into the wind'll only get you wet & smelly.
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:z78R9.121$g61....@news.uswest.net...
J Thompson
I looked thru some 5" and 6" models and the fastest one did not look all
that smooth a figure.
I think these were figured by double pass Ronchi.
Regards,
J Thompson
EJN
back up claims of quality with hard data.
As for buyers using it for boasting, not
my problem. I'm not responsible for their
behaviour.
Jan Owen
those days was worse than today, for obvious reasons, of course, but they
were still by and large excellent scopes. But today the consistency is
better.
I have an f/7 APO from Roland's pre-interferometry period, and it's no
slouch.
"J Thompson" <JTh...@hotmail.com> wrote in message
news:2H9R9.76463$xp4.3...@news1.telusplanet.net...
rande...@aol.com
I don't suppose your neighbour kept the test report from the TV-101?
-Rich
David Low
>The time has come for you to show with solid facts what it is that your
customers pay for...
I agree with Edward's sentiments (I would also like to see test results for
reflectors and catadioptrics), if not with his formatting. Objections I've
seen include:
1) "Ignorance is bliss". For you, maybe. So if you get a test report,
don't look at it - tear it up.
2) "Test reports would wreck havoc in the used scope market." Only if
certain premium scopes are uniformly inferior, or if there is a lot of
variance among samples of one scope. In either case, the flip side is that
there will be an incentive for manufacturers to produce uniformly high
quality instruments.
3) "Since test reports are difficult for amateurs to verify, economics would
encourage manufacturers to, umm, massage the results." Probably true, and
probably happens now.
4) "Red laser interferograms are useless for refractive optics." So insist
on green, and insist on a standard quality for reference optics.
5) "Amateurs aren't competent to interpret interferograms." Probably true.
So digest it down to a confidence range for Strehl ratio, e.g " 93% to 95%"
or "above 97%". Insert explanatory text so buyers don't panic over strange
numbers. Leave the raw data in the test report, though.
6) "Too expensive." So make it an added-cost option.
7) "You're a troll. You're an ego-tripper. Don't piss and moan." See 1)
above.
David Low
David Low
> Troll alert!...
> Those who cry the loudest that they want interferometry with their scopes
> almost invariably want it, not as a guarantee of quality, or as direct
> evidence of quality, but purely for bragging rights...
> All this pissing into the wind'll only get you wet & smelly.
Do a Google search for "ad hominem".
David Low
Eric Jensen
piece of paper with an interferogram -might- (in certain cases) not be
anything more than a sales trick to make the buyer feel good. How the
telescope performs in use is what counts.
Eric Jensen
mark d. doiron
news:z78R9.121$g61....@news.uswest.net...
> To Astro-physics, Televue, Takahashi
> and TMB USA (Thomas Back) Manufacturers:
> The time has come for you to show with solid facts
> what it is that your customers pay for.
Edward (and David Low and all the rest of you who agree with this):
please, if you're truly serious about buying one of these scopes, do so
and send it away to have it tested. if you're not satisfied, i'll bet
you dollars to donuts that the mfg will take it back (but, by all means,
let us know the details if they don't!). the rest of us aren't
interested in paying for this service, which even Roland Christen admits
is fodder for marketeers.
if you're not interested in buying one of these scopes (and i must
wonder why any owners of an AP would be!), then i suggest that you drop
your concerns about how my scope or anyone else's scope performs in some
useless test environment. it sounds too much like you're worried that
someone's scope may be outperforming yours and that doesn't really
matter: i'm happy with mine and i hope that you're happy with yours.
that's what is important.
clear, dark skies--
mark d.
HAVRILIAK
>> what it is that your customers pay for.
I find some of the previous disscusion humerous and reminds me of two points.
1. Don't confuse me with facts, my mind=0 is made up.
2. If we start testing high school students, teachers would start teaching for
the test.
In the second case this is not all to bad a result since its more than they
now know.
John Ford
Edward
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message news:z78R9.121$g61....@news.uswest.net...
To ASTRO-PHYSICS, TELEVUE , TAKAHASHI and TMB USA (Thomas Back) Manufacturers:
The time has come for you to show with solid facts ...>snip<
They are waking up from the apathy you induced and the soothing lullaby you print in your catalogs.Sincerely,Edward Hillyer
The problem with providing testing results with production model telescopes is a practical one. People will pay more for the best and less for the poorer examples. How do you sell two scopes, with significant differences in optical quality for the same price? Can you imagine each Tele Vue 102 being asigned a sale price based on it test results? A nightmare for retailers, manufacturers, buyers.If you sold these scopes for the same price, reguardless of specifications, you'd have people grabbing all the above average specimens and reselling them at a premium. Another nightmare. In the real world, its easier to have relative value be a bit more nebulous and let the buyer beware.Ed
Bill Bahus
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message news:z78R9.121$g61....@news.uswest.net...
To ASTRO-PHYSICS, TELEVUE , TAKAHASHI and TMB USA (Thomas Back) Manufacturers:
Drivel snipped
EDWARD HILLYER
Jan Owen
My comments remain unchanged.
"David Low" <davi...@acm.org> wrote in message
news:8ecR9.542246$%m4.1...@rwcrnsc52.ops.asp.att.net...
EDWARD HILLYER
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message news:YoiR9.13$5%5.4...@news.uswest.net...
EDWARD HILLYER
Skip Freeman
> What's up with that????
Well, I hear tell that some guys really get off on that kind of stuff.
-Skip
EDWARD HILLYER
Good bye and good luck.
Edward Hillyer
"Jan Owen" <jano...@cox.net> wrote in message
news:7riR9.33902$L61.2...@news1.west.cox.net...
Stephen Astro
Are you like a Phil Hendrie character?
Steve O.
ValeryD
> Finally, things are heating up a little since Valery pulled out!
>
> ... this ought to be good!
>
> - Don
Don, for your full of bull shit head, I have to say, that such werb as
"pulled out" is not valid about me and our optics. Not vaild at all.
Surely, soon enough you will see. And I will keep the copy of this your
idiotic message and always will show it to you.
For your, idiot, instance - the ARIES always shipped all large and
expensive optics with full interferometry data. And don't think you
pinched me by your idiotic message. The only reason I reply is that
to make clear, that I am still on the side to supply interferometrci
data with expensive optics. And we always will do this.
It will be interesting to know if such brave and boastful company as
your lovely SV will ever support their claims about quality by supplied
with each expensive telescope such a simple things as interferometry and
processing data.
Valery Deryuzhin
ARIES.
Jan Owen
If you really want to make a step-change improvement in commercial telescope
quality, maybe the energy would be better expended toward convincing Meade,
Celestron, Synta, and others, to provide interferograms for each one of
THEIR optical sets.
The problem with your approach is that the folks you are barking at are
already delivering some of (I didn't say all) the best scopes being produced
today. That isn't the area where wholesale improvement is needed, if,
indeed, a step-change improvement IS really needed.
It's also interesting that Meade, Celestron, and Synta are also delivering
quite good quality today, given the price points they work within. Of
course, the reason these folks don't produce 1/10 wave optics is because,
while many folks believe they are entitled to that level of quality, the
simple fact is that few are willing to pay the price that would result from
a requirement to consistently produce to that level of performance, and
provide individual interferometry to prove it. What folks get today, in
reality, is a bargain. Never before in history have so many really good
telescopes been available for such reasonable prices.
Providing Linus with a new security blanket won't necessarily enrich his
life...
Looking back in history to the late 1980's, a step change in industry
quality was indeed needed. During the Halley era, extremely optimistic
claims were being made, while actual quality was nowhere near this level,
and surprisingly many real stinkers were being released through the
manufacturer's quality assurance units. This is clearly not the case today.
Not every scope is of extremely high quality, but overall uniformity of
quality has improved dramatically, while prices are REMARKABLY low,
considering value received.
I believe we are looking at the result of that step change in industry
quality today, even though some exceptions continue to be reported here in
this forum.
I applaud your desire for universal high quality instrumentation, but I
doubt your proposed solution would make significant measurable change if
implemented.
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:QuiR9.16$5%5.4...@news.uswest.net...
Cover2Cover
- Don
Brian Wirthlin
Zeiss shuttered the amateur side of the Astronomical Division because
the cost to produce the APQs was twice the US List price, and the plan
to early retire everyone over 55 would require introducing a whole new
generation to the production process. Frankly the APQ design was a
labor of love, and the majority of the work was done before the wall
came down. Are they wonderful, yes I think so, but I can hardly be
described as unbiased. Obviously scopes of this quality can be
produced, but there is no empirical evidence that scopes of this
quality can be consistently produced for the amateur market
profitably.
Brian
You don?t always get what you pay for, but you rarely get more.
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message news:<z78R9.121$g61....@news.uswest.net>...
> --
godzilla
<snip crap>
Your personality is about as pleasant
as a deep rectal itch.
Chris1011
described as unbiased. Obviously scopes of this quality can be
produced, but there is no empirical evidence that scopes of this
quality can be consistently produced for the amateur market
profitably>>
Believe it or not, scopes of this quality are being produced, and profitably.
And they are definitely a labor of love.
Every lens made here at Astro-Physics has a test report made on a green light
interferometer. These reports are in a big fat folder, as well as on the
computer harddrive. I have taken them to star parties in the past (Astrofest,
Starfest in Canada, and Florida Star Party), and displayed them for anyone to
examine. Believe it or not, no one paid them any attention. Shall I bring
hundreds of them to Florida with me when I come?
I think in our case, what I may do is to provide a certificate for the owners
of the scopes that guarantees that the optic has passed some minimum level of
performance of RMS wavefront and Strehl ratio. We do already guarantee this
now, but not on a nice seperate piece of paper, suitable for framing (like a
college diploma).
Mr Hillyer has deftly sidestepped the fact that the red light interferogram
supplied by Zeiss is worthless (I covered this in other posts). I ask again,
what was the point of Zeiss supplying this interferogram if it was meaningless?
Can you answer that, Mr. Hillyer?? (hint: has something to do with marketing)
Oh, by the way, if you test a lens figured for the yellow-green wavelengths
with a red light Zygo interferometer, it will indeed test as barely diffraction
limited. Do you know why, Mr. Hillyer??
Roland Christen
Astro-Physics
Alan French
It is very hard to take you seriously. You obviously ignored the previous
discussion about red light interferograms.
Clear skies, Alan
"EDWARD HILLYER" <edward...@hotmail.com> wrote in message
news:z78R9.121$g61....@news.uswest.net...
[SNIIP[
ZEISS had it right when it gave EACH Maksutov and APQ apo new owner a Test
Report. Those scopes are STILL the most
[SNIP]
Alan French
got my scope and I was looking at the test report. My lens is 1/30 wave
RMS. My friend Bob has one of your lenses. His is 1/35 wave RMS. I want a
better lens."
Please don't say this wouldn't happen - because it has.
Clear skies, Alan
"EJN" <nos...@compusmurf.com> wrote in message
news:3E152B47...@compusmurf.com...
Alex Walls
> The real proof of telescope quality to it's owner, is at the eyepiece, not
> on a piece of paper. That paper means squat under the stars. The majority
> of observers wouldn't be able to distinguish between a 1/5 wave optic and a
> 1/10 wave one visually, so tell me what the interferogram really buys you.
> Squat. But it IS a meaningful system for testing an optic during
> manufacturing to ensure consistent quality.
Agreed. After all, it's not like we are talking HST primary mirror
accuracy. And even if we were, can you be sure the null corrector
is giving accurate results?! :-)
David Low
> What would you do when a customer calls and says, "I just
> got my scope and I was looking at the test report. My lens is 1/30 wave
> RMS. My friend Bob has one of your lenses. His is 1/35 wave RMS. I want
a
> better lens."
Well, first I wouldn't make distinctions that could disappear with a breath
of cool air, such as that between 1/30 and 1/35. Instead I would grade into
ranges, such as "better than 1/6" and "better than 1/10".
Secondly, I would charge extra for higher-performance optics.
This approach is being used by manufacturers in many industries. When I buy
a Pentium chip, they don't tell me that I have to guess the clock speed. If
I buy a 1.6 GHz rather than a 2.4 GHz, presumably it's because I have made
an informed decision as to my requirements and budget.
I'm at a loss to understand why so many amateurs are adverse to knowing more
facts about their optics. These are the same people who spend hours
agonizing over star tests, who avidly conduct highly subjective comparative
"shoot-outs", and who use bellicose terms to describe the results.
It may be that our hobby is more of a sport than a science, and that having
an objective optical analysis is like game-fixing.
David Low
Chris1011
facts about their optics. These are the same people who spend hours
agonizing over star tests, who avidly conduct highly subjective comparative
"shoot-outs", and who use bellicose terms to describe the results.
It may be that our hobby is more of a sport than a science, and that having
an objective optical analysis is like game-fixing.
David Low>>
I don't think people play games with their scopes. I think a lot of people just
use their telescopes for the purpose that they were constructed, and get good
results with them. Just visit any of the high end manufacturers' web sites and
peruse the gallery sections. These amateurs don't have time to argue about
theoretical performance or test report data. They see what can be done with a
particular scope, be it SCT, Refractor, Newt or Mak, and if it fits their needs
they go with it. Most, if not all, the high end manufacturers do their damdest
to produce, or have optics produced, to the highest quality level possible with
today's technology. I've seen very few lemons and a lot of satisfied people at
star parties. The bad companies get weeded out pretty quickly.
Roland Christen
David Low
> Edward,
>
> It is very hard to take you seriously. You obviously ignored the previous
> discussion about red light interferograms.
I dunno, it seems to me that Edward's adulation of Zeiss is something of a
red herring (sic), not having anything to do with his advocacy of
interferograms for new scopes. If RC demonstrates that Zeiss had a
questionable testing methodology, does this mean there's no need to test
these days?
And, while I'm soapboxing, I'd like to suggest that refractor manufacturers
also publish data on secondary spectrum, although this may not be needed on
a per-unit basis. It would be great to be rid of terms like "semi-APO",
"super-APO", etc. As far as I know, AP is the only manufacturer that
provides this information.
David Low
Alan French
I am not adverse to knowing more about the optics I buy, but my main
criteria is how well a system performs in focus under the stars. I have a
very nice lens that came without any test report. It has, however, proved
itself in actual use, and has generated many, many nice comments for people
who have looked through it. I don't think having a piece of paper with some
numbers on it would have changed anything.
Your approach might work, but I think a lot of folks want to know exactly
what they have. Unfortunately, there are folks whose expectations exceed
reality. I know one gentleman who returned a very fine scope because the
numbers did not seem quite good enough to him.
Clear skies, Alan
"David Low" <davi...@acm.org> wrote in message
news:HKlR9.548578$P31.182453@rwcrnsc53...
> [SNIP]
> I'm at a loss to understand why so many amateurs are adverse to knowing
more
> facts about their optics. These are the same people who spend hours
> agonizing over star tests, who avidly conduct highly subjective
comparative
> "shoot-outs", and who use bellicose terms to describe the results.
> [SNIP]
Alan French
I sure agree with you here. It is odd that they don't provide this (well,
perhaps not), since all it takes is one amateur willing to write a check to
Edmund Scientific and buy a few narrow band interference filters to actually
measure the variation of focus across the visual spectrum. I almost did
this, but then realized I had no lenses I wanted to test and was certainly
not interested in getting into the telescope testing/review racket.
Clear skies, Alan
"David Low" <davi...@acm.org> wrote in message
news:V9mR9.548855$%m4.1...@rwcrnsc52.ops.asp.att.net...
> [SNIP]
Brian Tung
> I'm at a loss to understand why so many amateurs are adverse to knowing more
> facts about their optics. These are the same people who spend hours
> agonizing over star tests, who avidly conduct highly subjective comparative
> "shoot-outs", and who use bellicose terms to describe the results.
I'm not sure that they are the same people. Probably those people *do*
want test results, and they want the best test results. They are also
beset by Golden Eye and Empty Pocketbook Syndromes. (Pride and price
split hairs.) Many other people see that the way they use their scopes,
the places where they use them, and the times they use them, are peculiar
to themselves and can't be standardized for testing anyway.
It's not the same as a computer, for example, where if it runs at 1.6
GHz one day, it will run at 1.6 GHz the next (more or less <g>). The
atmosphere introduces such a random factor that such precision is not as
useful as it might be otherwise.
Personally, I think that test results are nice, but those who can read
them and understand them probably know enough about real-time use that
they could tell a bad scope pretty easily, and those who aren't that
experienced may not understand the test results. What I'd like to see
is some sort of Good Housekeeping seal, but I haven't a good idea how
that would be implemented.
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
TMBack
First Edward, I don't mind what you say about me, but thanks for
spelling my name right.
You may be surprised to learn that TMB lenses are set to the same
standard as the Zeiss APQ lenses: Strehl .95 or better, and in our case,
unlike Zeiss, we use green light interferometery, the correct wavelength
to test refractive and compound optical systems.
Zeiss' use of red light (632nm) testing was a mistake on their part, as
it does not provide the information needed to determine the wavefront
quality where the eye is sensitive to the greatest detail, in the green to
green-yellow. What it is measuring is the amount of spherochromatism,
plus any other phase errors at 632nm at the wavefront. To be exact, due
to refocus, it doesn't measure the amount of OPD error at 632nm that the
lens has when it is at best focus at the eye's peak sensitivity, however, it
still cannot tell you or anyone else how the Zeiss lens performs at the
visual peak. As Roland said, it was a marketing tool.
None of the above says anything about the quality of the APQ lenses,
which were some of the finest optics ever made for the amateur market.
Their "secret" was simple. The use of a good triplet glass combination
(BaK-2/CaF-2/K-11 -- there are better combinations), long focal ratios
in all but one model, excellent polish and coatings, a superb (in the later
models) cell design, and a master optician that hand figured each lens in
white light. Sounds a lot like Astro-Physics and TMB.
Like John Ford and Alan French said, there were cases of people demanding
a new lens and in other cases wanting refunds. For the first two years, TMB
Optical sent out the test report in the manual. I have never sent out a lens,
in
what is now almost five years, that wasn't better than Strehl .95. In fact, the
average lens is considerably higher. Not only that, but each lens is tested by
me personally with a large flat in autocollimation, and a final real world star
and (if possible) planetary test.
But the numbers game took over, and even tiny differences in the test reports
(like a Strehl difference of only .05!) from their friends TMB or by word of
mouth would have an angry customer that wanted either a new lens or his
money back, even after I asked them if they saw anything wrong with the
lens after testing it on the Moon, planets, double stars and the star test. The
answer was always no, that it was superb visually, but they felt they needed
that paper that had higher numbers. The other problem is that everyone's test
setup is different, and comparing interferograms, or test reports from one
company to another, will never be a level playing field. This is not to say
that
any company is fudging their numbers, in fact, I believe they are trying their
best to get the most accurate numbers possible, but because of the over-
whelming variables in any testing setup, it is nearly impossible to expect that
one optic wlll give the same numbers in 10 different optical testing tables.
Carl
Zambuto has had some of his mirrors tested interferometrically, and the
results are different from his own testing. This is just one example.
Well, sending the test reports out became a monster, and I didn't want to do
it,
but I had to stop sending the test reports. I have every lens sold on file,
with the
customers' information, serial number, and comments about my visual testing
of each lens. The real test of any telescope is out in the field, not on a
piece of
paper.
Thomas Back
TMB Optical
EDWARD HILLYER
customers.
Same from AP!
Now let's see if Televue replies and what they say. Can't do much when those
lenses come from Taiwan, and the scopes are only assembled here in the
USA...
"TMBack" <tmb...@aol.com> wrote in message
news:20030103155009...@mb-mp.aol.com...
Vahe Sahakian
> customers pay for. You expect us to pay thousands of dollars for one of
> your Telescopes and tell us simply its "diffraction limited " in Televue
> case, or "1/10 wave lenses" in the case of AP?
I have in front of me two printed telescope literatures, one is from
Zeiss, a full page test report on their APQ 100/1000, Zeiss claims a
Strehl of 95% for this lens, the second test is for an imperted 6"
Maksutov Cassegrain with 35% central obstruction, its manufacturer
claims a Strehl of .97.
My question to you; how is the average amateur going to interpret
these numbers? Or, if we go by test numbers alone which one in your
opinion is the higher quality telescope?
Thanks,
Vahe
David Low
> My question to you; how is the average amateur going to interpret
> these numbers?
It seems you are implying: "Information can be misleading, misinterpreted or
wrong. Therefore we should not have any information."
This seems to be the approach of some contributors to this saa topic.
I prefer: "Information can be misleading, misinterpreted or wrong.
Therefore we should endeavor to improve the quality of information and to
help the user interpret it."
So, to answer your question, you include information sheets that instruct on
what Strehl ratio means, details on the test methodology and how the results
can be interpreted.
David Low
EDWARD HILLYER
correction more clearly.
The MAK may have strehl 97, but the secondary's presence will always prevent
it from performing better than 1/4 wave at the focal plane.
The APQ 100/1000 will have at the focal plane at least overall correction of
1/10 to 1/12 wave with that strehl.
"Vahe Sahakian" <va...@flash.net> wrote in message
news:282f6d47.03010...@posting.google.com...
DGM Optics
Hi Thomas,
I would concur that your bottomline is indeed *the* bottomline regarding a
specific instrument of any design. Interferometry is only a good indication
of how an instrument might perform, but certainly not an absolute
declaration of such.
In my own experience manufactoring off-axis newtonian reflectors we "cut"
smaller off-axis primaries from a larger "parent" mirror. My optician is
quite skilled with this type of optic and produces generally speaking very
high quality mirrors. He uses a Double Pass Fizeau Interferometer for the
figuring process. However we have had instances where a set of off-axis
primaries from the larger "parent" have tested with numbers typical for his
quality of work but had very subtle annular zones that could not be detected
from the interferometry. These zones if present in the uncut parent mirror
would in my opinion be nearly undetectable in a star test but with the
off-axis primaries are manifested as "arc swaths" that are not concentric
with the fresnel pattern and tend to throw energy out of the last
diffraction ring or in some instances what I can best describe as dividing
the energy in the last ring. Interestingly, if the energy in the last ring
is "divided" more or less equally it has almost no effect on the in focus
image but if not as the ring(s) reduce to the focal point it becomes almost
astigmatic or triangular (reminiscent of pinched optics) then when in focus
the Airy-disc will have a slight spike on one side.
So had I not tested these optics under the stars and relied only on the
interferometry I would not have spotted it and someone would have received a
subpar instrument (but very good interferometry numbers to go with it!)
Dan McShane
www.dgmoptics.com
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ValeryD
You both (with Cover2Cover) are real duet of idiots. You both sing
so harmony, that I think you are the same big piece of bullshit.
Victor Kennedy
Track or Car and Driver, I can't remember exactly which one, an
interview with a representative of Rolls-Royce, who when asked the
horsepower of the latest Rolls-Royce, answered "adequate". When
pressed further, he said that peope who buy Rolls-Royces don't care
about numbers.
Siegfried Gonzi
> Same from AP!
> Now let's see if Televue replies and what they say.
What will you expect from a company who advertises their Pronot/Ranger
achromat line as ED scopes?
S. Gonzi
Thomas
<edward...@hotmail.com> wrote:
>This is a multi-part message in MIME format.
>
>------=_NextPart_000_0012_01C2B2A4.215C8F50
>Content-Type: text/plain;
> charset="Windows-1252"
>Content-Transfer-Encoding: quoted-printable
>
>To ASTRO-PHYSICS, TELEVUE , TAKAHASHI and TMB USA (Thomas Back) =
>Manufacturers:
>
>The time has come for you to show with solid facts what it is that your =
>customers pay for. You expect us to pay thousands of dollars for one of =
>your Telescopes and tell us simply its "diffraction limited " in Televue =
>case, or "1/10 wave lenses" in the case of AP? Until YOU supply an =
>Interferometry Test Report with each scope you sell, you expect =
>consumers to be pulled by the ear around a circle and believe IN FAITH =
>in your advertisements ? Words are cheap. Lab Test Reports are what you =
>SHOULD provide. (Star tests DO NOT tell the whole story.)
>In fact , it would be economical for you in the long run, and =
>profitable, if you REALLY are selling/making optics to the level you =
>promise, to provide proof with each scope.=20
>ZEISS had it right when it gave EACH Maksutov and APQ apo new owner a =
>Test Report. Those scopes are STILL the most expensive on the market , =
>even after the Amateur Telescopes section closed in late 1995.=20
>No one can match what Zeiss did optically, and you know it!
>But at least give your buyers a Test Report from Interferometry, and =
>don't tell me "but then each owner would claim<< my scope is better than =
>his/hers, theirs, >>etc" No excuses please.
>It's time the whole truth comes out. When I worked at Lumicon I HAVE =
>SEEN on our neighbors Zygo (he's making optics for the military) a =
>TV-101 BARELY being diffraction limited. Seen a TAK FS102 a little =
>better than that, another FS102 really good, an older AP 6" exactly at =
>the diffraction limited performance , but no 1/10 wave at the film =
>plane, no sir.=20
>And don't tell me I don't know what I'm talking about. I spent the last =
>several years researching this issue and testing your claims.=20
>Start delivering what you promise by supplying your consumers with an =
>Interferometry Test Report, and show them what they are getting. Don't =
>treat consumers like they are gullible. They are waking up from the =
>apathy you induced and the soothing lullaby you print in your catalogs.=20
>Sincerely,
>Edward Hillyer
>=20
Oh it's the old argument about whether a 100 watt stereo by Panasonic
is better than a sony 100 watt stereo....unless your a professional
astronomer or a serious "amateur" who knows exactly what they are
looking for and what it should look like up thar...your just another
one wasting your time on matters that are meaningless...
D.E. & D.K. Cobb
I you don't like what these manufacturers do, then don't buy their
products. The manufacturers are in business to make money, not to
appease trolls. If the market dictated that test reports boosted
sales, these scopes would come with test reports. Apparently, that is
not the case. Anyway, I enjoy looking *through* my A-P and Tele Vue
much more than looking at test reports. If I can't *see* a
difference, it doesn't matter to me (i.e. why should I be worried
about numbers on a slip of paper?)
Danny Cobb
David Low
to know what they're buying before they buy it:
I just checked my three-year old copy of Suiter. When I got this volume, it
was already in its fourth printing!
So it seems that, while you may be disinterested in scope testing before you
buy, you're certainly concerned AFTER you buy.
May residual spherochromatism bring color to your cheeks this new year,
David Low
EDWARD HILLYER
Tets does NOT tell the whole story.
"David Low" <davi...@acm.org> wrote in message
news:xWDR9.440713$GR5.1...@rwcrnsc51.ops.asp.att.net...
David Low
> The well-respected optician/tester Mike Palermiti in Florida says ...
It's hopeless, I surrender.
David Low
Brian Wirthlin
Roland,
It was not my intention to demean your products. I was attempting to
rein in the best/bang/buck/bullxxxx. I occasionally get calls from
people interested in the APQ line. After explaining that they are no
longer produced I recommend Astro-Physics. There are many tradeoffs in
design, manufacturing and marketing. You've been unfairly taken to
task here for decisions in all three on various occasions. But it's
the market place that ultimately determines which of the multitude of
permutations are viable. In the end analysis Astro-Physics is still
producing, evolving and improving their telescopes. Good, bad or
indifferent Zeiss is not.
Brian
Edward
Vahe Sahakian
> Therefore we should endeavor to improve the quality of information and to
> help the user interpret it."
I have been around for a while, I do remember the Halley comet days,
in those days you could buy a 12" mirror 1/10th wave for a price, but
if you preferred 1/20th wave, hey, "no problem we have it, same price"
how about 1/30th wave, same price.
Never, never underestimate the skills and creativity of the average
manufacturers, if it becomes necessary to provide the test results to
sell and survive, they will find a way do it, the BOTTOM LINE is that
it is YOUR responsibility to verify these numbers and challenge their
manufacturers, and, very very few amateurs have the resources or are
willing to spend the $$$ to have their scopes tested by a qualified
third party optical testing lab.
Personally, I have chosen the manufacturers reputation, and, so far I
have not been disappointed.
Thanks,
Vahe
Alan French
I think many amateur astronomers have a pretty darn good idea which
companies make quality products.
Clear skies, Alan
"Vahe Sahakian" <va...@flash.net> wrote in message
news:282f6d47.03010...@posting.google.com...
> [SNIP]
John
Well I'm convinced. I'm going to unload that Hillyard piece of crap
TV 85 I've been so happy with at an appropriately crappy price on
Astromart right away and get on the 2 year wait list for a new AP.
Maybe by then it will clear up in Connecticut.
EJN
> I'm just curious. What would you do when a customer calls and says, "I just
> got my scope and I was looking at the test report. My lens is 1/30 wave
> RMS. My friend Bob has one of your lenses. His is 1/35 wave RMS. I want a
> better lens."
Well, turning the question around, what if there was
no test data, and a customer said his friends lens
has a better star test, and then wants a better one?
Seems one way or another you can't win.
Rod B.
that is where the worth of the specification lies. In any measurement
process, it's the standard of methodology that counts. Part of the reason
that amateur optical specifications have never meant anything is because
there have never been any universally accepted (or mandated) standards for
testing...and no affordable amateur access to real testing.:-)
Rod B.
David Low wrote in message ...
Alan French
majority of folks are quite happy to have a quality scope and are enjoying
looking at in-focus images. Unfortunately, I suspect a lot of fussy folks
have rather inflated ideas about their ability to star test, expecially when
it comes to the more exotic designs.
Snowy skies, Alan
"EJN" <nos...@compusmurf.com> wrote in message
news:3E168B91...@compusmurf.com...
godzilla
>...real duet of idiots...
>...same big piece of bullshit...
I know you are, but what am I?
Victor Kennedy
I'd be happy to take it off his hands.
clyde crewey
Actually I've read Suiter before and after I got my TV85. The 85 tests
very well. I didn't buy it for that reason however. I already had a
Ranger and was very pleased with the performance of that scope. I
also loved the TV eyepieces I owned. So it was icing on the cake when
I called up Televue and not only got Al Nagler on the phone, but found
him to be a frank, honest and friendly man. And while I don't know
what the wavefront number is, I do know these things:
I have used my TV85 almost daily since I got it last spring. I enjoy
nature viewing as well as astronomy so it sees a LOT of use. I throw
it over my shoulder, hop on the subway and go to Central Park where
one can observe Screech Owls, Peregrine Falcons, Red Tailed Hawks and
all sorts of other NY creatures.
It splits the Trapezium into 4 sharp dots in a TV 32 Plossl. That's
19x.
It has shown me the F star in the Trapezium at 115x
Once with the sun almost directly in our faces, a birding friend
couldn't identify a bird in his Swavorski's (sp?). One glance in the
TV85 made it easy.
It has shown me 3 craterlets in Plato (counting the doublet as one).
But no, I haven't seen the Central Rille in the Alpine Valley. Nor
with my 6" Dob.
At 66x, Saturn's Cassini Division is sharp and banding on the planet
is apparent. It only gets better up to 214x, when it starts to run
out of light. I've seen 5 moons with direct vision.
The double double splits at 60x.
The GRS is easy starting at 66x and shadow transits are razor sharp.
I've followed transitting moons over 1/3 of the way across the planets
surface before losing them.
I could go on (and on!) but you get the drift. I observe from my
rooftop in Manhattan by the way, which makes it's performance all the
more impressive. I use my scope a heck of a lot and it's been easily
worth what I paid for it. What do you want from your 85mm scope?
Happy observing!
You do observe don't you?
Clyde
"David Low" <davi...@acm.org> wrote in message news:<xWDR9.440713$GR5.1...@rwcrnsc51.ops.asp.att.net>...
D.E. & D.K. Cobb
You cannot possibly know whether your TV-85 is good or bad anymore than I can know if mine is good or
bad. Neither came with a TEST REPORT. :^)
Danny Cobb
David Low
> Actually I've read Suiter before and after I got my TV85.
I have a TV85 too. It's a fine instrument, and I use it more than any other
scope. I wouldn't feel threatened if it came with a test report, and I
can't imagine why you do.
> You do observe don't you?
Yet another snide, 'ad hominem' remark. You see these a lot when people
can't think of cogent arguments.
You can think, can't you?
David Low
ValeryD
> >...real duet of idiots...
> >...same big piece of bullshit...
>
> I know you are, but what am I?
I think you are even more stupid than this can be concluded from
your short posts. The last case show me that you are not able
to not mixture the simplest things. I try to explain again:
_you_ are a part of that big piece of a bullshit.
clyde crewey
LOL! Where to start?? Let's tackle snide first. A certain poster
with the moniker Max the Woo recently posted a question about why he
was getting a certain image. A certain David Low responded and I
quote:
"I dunno. Perhaps because you've forgotten your medication?"
Now if that David Low wasn't you, well then ignore the above. If it
was indeed you however, calling any other poster snide is at best
hypocritical don't you think? Especially since my question to you
about observing was half serious.
Why would you infer that I would feel threatened had my TV85 come with
a test report? Am I safe then in inferring you would have felt
re-assured had yours come with one? If so, why? Mine splits double
stars at the theoretical limit so no test report would change that.
There was a lot of written and photographical evidence easily
available on the TV85 before I bought it, so I was hardly purchasing
an unknown quantity.
I assume your TV85 is still under warranty. Send it back and ask them
give you a wavefront number if that'll make a difference to you.
Though if yours performs like mine I don't see the need to do this.
Resolving Dawes Limit is a pretty good test. I spent too much time
before I got my scope analyzing and reading endless reviews and
researching. In hindsight, I would have been better off to have gone
ahead and purchased when I originally meant to. My eyes lost a month
of their lifespan. And I can't get it back.
Keep enjoying your scope. No more snide comments from me.
Clyde
"David Low" <davi...@acm.org> wrote in message news:<ryXR9.571552$P31.199219@rwcrnsc53>...
Gary Moors
in green light if one knows the strehl ratio using red light. So, for
example, if we have the strehl from a specific Zeiss APQ using red
light of 0.98, is there a way (without testing) to calculate the
strehl for green light? If not, has anyone tested a Zeiss APQ in green
light so that we can all know where they fall for more realistic
comparison purposes?
Thanks,
Gary
tmb...@aol.com (TMBack) wrote in message news:<20030103155009...@mb-mp.aol.com>...
> >To ASTRO-PHYSICS, TELEVUE , TAKAHASHI and TMB USA
Brian Tung
> I would like to know if there is a way to determine the strehl ratio
> in green light if one knows the strehl ratio using red light. So, for
> example, if we have the strehl from a specific Zeiss APQ using red
> light of 0.98, is there a way (without testing) to calculate the
> strehl for green light? If not, has anyone tested a Zeiss APQ in green
> light so that we can all know where they fall for more realistic
> comparison purposes?
For purely reflective systems with reasonably small errors, you should
be able to transform one to the other. A 550 nm Strehl should be worse
than a 650 nm Strehl, with the dropoff from 1.0 about 40 percent larger,
so that if the 650 nm Strehl is 0.90, the 550 nm Strehl will be 0.86 or
so.
For systems with at least one refractive element (such as a lens), I
can't see how there would be a straightforward way to do it, but perhaps
someone else here knows a way.
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
EDWARD HILLYER
in green.
"Gary Moors" <gar...@voicenet.com> wrote in message
news:d2adf55a.03010...@posting.google.com...
Enyo
particular aberrations then an optical designer can do it. After all it is
not magic but only very well understood optics. And no I could not do it.
"Gary Moors" <gar...@voicenet.com> wrote in message
news:d2adf55a.03010...@posting.google.com...
Max The WooWoo
>Let's tackle snide first. A certain poster
> with the moniker Max the Woo
That's two woo's pardner.
<gunplay ensues>
Max "Whaddya mean I can't load my 80mm?"
David Low
> The manufacturers are in business to make money,
> not to appease trolls...
> If the market dictated that test reports boosted
> sales, these scopes would come with test reports. Apparently, that is
> not the case.
As far as I can determine, all Ritchey-Chretien manufacturers supply
interferograms with their scopes. Of course, these are expensive
instruments and the "market" is driven by very serious amateurs.
It's obvious that many on this thread do not have a need for test reports.
Fine. But serious amateurs may ask for the same accountability from a $10k
Tak that they get from a $12k RCOS. Why do you feel the need to
characterize these people as trolls and poseurs?
David Low
Markus Ludes
From: "EDWARD HILLYER" <edward...@hotmail.com>
Subject: Re: LETTER TO AP+TAK+TELEVUE+TOM BACK (TMB)
Date: Sun, 5 Jan 2003 14:50:28 -0700
--------------------------------------------------------------------------------
What I know from my calculations is that 1/8 wave pvt in red is 1/7 wave
pvt
in green.
M. Ludes:Edward, thats pur speculation without any background reason. If
A APQ is nulled at green and they are for shure nulled at green, than a
red tested 1/8 wave APQ will be better than 1/8 wave at green and not
less good
Markus
--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
Bob May
be many waves out of shape at different colors and define the shape of it at
one color? And then compare that to a reflector which is color free?
Nah, I don't think so.
I'll also note that the errors of a refractor are not so much with the
actual construction of a design but rather the design itself. You can have
a lot of errors in the surface shape of a lens and the ultimate errors
procuced are very small.
--
Bob May
Why is there an Ozone Hole at the South Pole but Not at the North Pole?
Somebody's been lying to you!