RE: [APML] Opinions on Borg 100mmED vs. Tak 102-106 (was TV-85 vsTaks)

["D. Kodama" <kodama@alumni.caltech.edu>]

Alan,

I shoot with the Borg 100ED and am very happy with it.  I have the f6.4/f4
combo configuration for medium format and normally shoot 6x7 format.  But
I also tried a few 4x5 shots:

  http://www.eanet.com/kodama/astro/010824a/    (4x5 @ f/4 and f/6.4)
  http://www.eanet.com/kodama/astro/2003/0103/07.htm   (6x7 @ f/6.4)
  http://www.eanet.com/kodama/astro/2003/0329b/11.htm  (6x7 @ f/4)

Sorry, the 4x5 shots are not of the highest quality as they were my first
shots, but they do give one a good idea of the image flatness and
vignetting performance of the scope in both configurations.  The 6x7 f/6.4
shot is actually a bit vignetted due to the use of a Pentax bayonet
coupling, but the f/4 shot is not because a special wide coupling was used
(as was the case for the 4x5 shots).  I'm very happy with the minimal
vignetting as I don't like to do vignetting corrections after the fact and
clearly, for 35mm or even 6x7, vignetting is very minimal if you use the
proper camera coupling.  A graph of the f/4 performance is available here:

  http://www.sciencecenter.net/hutech/borg/techdocs/100.pdf

Personally, I feel that vignetting performance is an important factor as I
think the film should be exposed until the sky background is becoming
visible on the film for maximum sensitivity as well as for ease in
scanning a positive film.

Dave

P.S. If you have any questions, CC me directly as I'm on the digest list
which causes a 1-day delay in delivery.




> Date: Thu, 14 Aug 2003 12:05:45 -0700 (PDT)
> From: Alan Voetsch <critter12952@yahoo.com>
> To: Discussion of Film Astrophotography <astro-photo@seds.org>
> Subject: [APML] Opinions on Borg 100mmED vs. Tak 102-106 (was TV-85 vs
Taks)
>
> --- Gene Horr <genehorr@houston.rr.com> wrote:
>> Personally I would discount the hot spot issue unless you
>> shoot from a light polluted area.  All of the prints I've
>> seen where taken from dark sites and no vignetting is visible.
>
> So far my skies are still pretty decent, but they get a little worse
> every year.
>
>> I would more compare the extra speed, smaller length, and
>> larger format coverage of the 106 with the 102 and decide
>> based upon that whether it is worth the extra money.
>
> I'll do that. Extra speed usually means wider field of view. That is not
> necessarily important to me. I like close up shots of stuff a lot.
> That's one reason why my most used instrment is a 12" SCT.
>
> The Borg 100mm ED has also been recommended to me. Anyone shoot with
> that, or a similiar instrument? If so, I'd like to hear any comments you
> might have.
>
> Thanks,
> Alan



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