Re: Best possible design for Fluorite doublet APO?
From: Tom Davis (tdavis11_at_carolina.rr.com)
Date: 11/24/04
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Date: Wed, 24 Nov 2004 14:59:32 GMT
Valery,
Not correct. I see ZERO color in-focus on Vega, the
same on Sirius. All I see is the barest trace of color
OUT-OF-FOCUS on Sirius, and it is so slight to easily
be missed. ZERO color any any daylight object or any
streetlight, and I have the worst offenders on my street
for brightness.
Please do not try to put words in my mouth. It won't
work here. All I see is a continued effort from multiple
fronts to belittle this lens. I have reported quite accurately
what I have seen. My first few days using this scope I
had to use an extension tube which was too short for the
scope. The original tube was designed for a 600mm FL
lens (the production lens is 700mm that is in this scope),
and this required both the diagonal and the extension tube
to be partway out of the scope. This created collimation
issues. With a proper length extension tube this went away,
and allowed for much better test results. With a proper
extension tube (3.5"), it works as I describe above. At no
time did I see any color on Vega in-focus, even with a short
extension tube. Currently, I can see none out-of-focus on
Vega with the scope properly collimated. I also needed to
align the prototype lens cell as well. William Optics had
cut the holes too large for where it attached to the rear part
of the cell, and created a decentering issue. I fixed that.
If anything, production mechanics would have only improved
upon my test results.
What you describe does fit my Orion 80ED. It shows some
small color on Vega, as well and bright daylight objects,
in-focus. The daylight view is the same as a reflector with
the 92mm Fluorite, while the 80ED is clearly seen to be
less than a true APO.
I have no financial interst in this scope. If it fails, I still have
a good scope that I paid for, nothing given me here. I did
not have to buy this scope. I could easily have sent it back
to Bill, as all he wanted was my opinion on it, and in fact,
I had no desire to buy it before I looked through the scope.
When I saw what it could do, I then asked Bill to sell it to
me, as he basically said it was going to be thrown out when
he was finished with it (scratch in the lens, which I sealed).
I offered him his cost for the scope, and he took it, that
simple. I felt I offered him a fair price, and so did he.
I am going to flip this one around the opposite way from
the way I am getting criticized. Until this scope gets into
other's hands stop trashing me here. Where I come from
you are innocent until proven guilty. If you had someone
on trial in court, and a tag team of the best prosecutors
working on the defendant, with no legal representation,
that would be called a msicarriage of justice.
I stood up for you Valery with the whole Chromacor
situation. I don't deserve this treatment from you. Let
this one go. The most anyone can say here is we need
to see what the volume production run turns out to be,
but that is a given with any product. I fully expect that
there will be those that decide to be conservative, but
since I had the chance to actually use the product in
question, I chose to buy it. But then that is what money-
back guarantees are for, and Bill does honor his.
Thanks, Tom Davis
"ValeryD" <aries@mercury.kherson.ua> wrote in message
news:5c4a4ee7.0411240120.18f4a2d2@posting.google.com...
> Somewhere else, Tom Davis wrote about promised 91.8mm
> Fluorite refractor.
>
>>What Thomas added by posting
>>the design, was credibility to what was being sold here, which was
>>not just a fluorite refractor, but a fluorite refractor with the
>>best possible design, and at a very low cost. My observations
>>through this scope don't contradict that in any way.
>
> Key words "best possible design". This is not true at all.
> With the best possible design of fluorite doublet with such
> small diameter and it's focual ratio, you will never see any
> trace of violet on Vega or Venus or even brightest street lamps.
>
> In your report you mentioned about smallest visible violet.
>
> In best possible design you will not be able to see (in focus)
> any trace of false colors on any object in thousands times
> brigher, than Vega in much larger Fluorite doublet, like our
> ARIES 7" F/7.7, not saying about total absense of trace of
> colors in such tiny 90mm doublet.
>
> This design, probably, is the best possible for China.
>
> We already heard from Bill Burgess, that his 127mm F/8
> achromats were made with 1/20wave(!!!!!) precision. What
> were in the reality? Just decent achromats.
>
> Please, try to escape to use such words as best possible,
> especially because you don't know exactly the subject.
>
>
>
> VD
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