Re: Notorious "SEMI-APO" term used again.

From: Tom Davis (tdavis11_at_carolina.rr.com)
Date: 11/24/04 

Date: Wed, 24 Nov 2004 15:13:51 GMT

Valery,

Please make Roland his eyepieces and stop trying to stir
up meaningless controversy. I don't think that 3X color
corection improvement (which is what the TMB design
on the new scope called the Burgess/TMB Semi-APO
provides) is out of the question to be discussed as a
semi-apo. I know what Vic Maris sold. Thomas Back
has designed a few lenses that have color correction far
better than the scope in question from StellarVue. The
color correction on the scope Vic called an EDT was
nowhere near the level we are discussing here. In that
case, it was a triplet, but it did not have much more that
achromat correction, due to the design and glasses used.
The term semi-apo would not really have applied there,
and the use of the term "EDT" was unfortunate, as it did
not use ED glass. In this case the term semi-apo is correct,
as it does provide enough improvement over a well-corrected
achromat (3X) to make the term have merit. Anyone
looking through this scope would readily see a marked
color correction improvement.

I really think that if you choose to address anyone on this
subject, address Thomas Back. He chose the name, and I
think he might have an idea of the difference between an
achromat and an APO. He has designed at least a few of
them that are in happy customer's hands.

Thanks, Tom Davis

"ValeryD" <aries@mercury.kherson.ua> wrote in message
news:5c4a4ee7.0411240137.4a9cd47f@posting.google.com...
> 7450 From: dhennig2 <dhennig2@t...>
> Date: Tue Nov 23, 2004 1:00am
> Subject: Re: 92mm Fluorite - clarification on definitions?
>
>
> Something here is really frustrating me.
>
> First, Tom, congratulations on getting a fine scope. The shots
> through it are most interesting...
>
> Now - it's the term "Semi-Apo" being used for this fluorite scope. I
> recall many months ago [about 2-1/2 years to be exact] that Vic Maris
> of Stellarvue was roasted fiercely by several parties eluding that
> his 102EDT f/6.1 triplet refractor could be dubbed semi-apo. There
> were rants all over SAA, the SV Yahoo! group, and elsewhere, scathing
> SV for using such a term.
>
> Interestingly enough, it was also a time when Tom Back got everyone
> to think of scopes in terms of either APO or achro performance, based
> on their color performance and spot behavior throughout the spectrum.
> There was a LOT of talk back and forth regarding this, then a hot
> topic amoungst refractor afficiandos.
>
> Why now is the term Semi-Apo being allowed to pervade the marketing
> once again, and what right does the likes of WO and BO [and for that
> matter TMB] have to use this "iffy" term now, when not even 3 years
> ago it was considered a false marketing term that did not mean
> anything?
>
> I just find it very interesting that all of a sudden, this seems okay
> for everyone with a Chinese-made optic. It seems very hypocritical to
> me. Some of the members here are ones who did the initial stuff
> against Stellarvue [SV] for this, and now its okay. Not fair!
>
> I suggest that someone here [Tom?] pin this issue down tight, else
> risk flooding the refractor marketplace with seemingly meaningless
> terms.
>
> Darren.
> ======================================================================
>
> Darren, I do understand you NOW. But, one question - were you was
> at that time? You suppported "semi" camp? ;>)
>
> It was not fair in a past, it is not fair now and it will be not fair
> in a future.
>
> Note, that WO already used this notorious term to increase selling of
> their plain achromat (Mrgrez-I) and they pioneered such apporach to
> color correction "improvement" and hidden internal aperture stop.
>
> It was then used in BO prototype 102F/6 - to hide poor edge performance
> and improve color correction.
>
> One of SV scope also was made with internal color correction improver
> and another one with "special" formula - notorious MV cut filter inside
> of it's objective.
>
> What will be the next trick to foolish the public, which still believe in
> magic in optics - in magic from peoples, who don't know the optics!
>
>
> VD

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