Re: [APML] Question about SCT and Giant Eazy Guider

[André Walczak <andre_walczak@gmx.net>]

Aloha Wei-Hao, hi Group,

>This makes me wonder if 35mm camera is
> its real limit and exactly how much I can get on a median-format
> film holder.

Me too! ;-)
I'm really addicted to medium-format and i'm always on the search for a
cheap possibility
to get longer focal lenghts for my medium-format cams!
So, I even had the idea to find out, whats possible with an SC, too.

   > I know that SCTs all have highly curved fields.  Does the
   > Lumicon focal reducer also serve as field flattener?

So, you mentioned the curved field, which of course is a big problem, but I
think
if you use a reducer, which will only reduce the focal lenght, the curved
field will be more curved!!

Because of this, I think to get this image quality which Philip shows on his
Webpage, the Lumicon
Reducer must work as a field Flattener, too.

But, because of the limited field a SC can provide, even when it's one with
11 or 14 inch, a reducer
could cut off a the light you would need for a larger format.
Things brings us to another Problem, becaue the focus of a series SC with
two spherical Mirrors suffers from
coma an astigmatism an of course the curved field.
So a focal-corrector with no optical power could help to make a SC usable
for larger formats.
But a SC with an aspheric secondary and perhaps a larger Baffle could even
bring more sharpness to the entire Field.
In combination with an focal corrector, I believe, such a system could even
bring the same performance as an RC System for CCD Imaging, but for a
cheaper price.

clear skies and greetings from rainy germany,
André Walczak





----- Original Message -----
From: "Wei-Hao Wang" <wang@IfA.Hawaii.Edu>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Sunday, June 20, 2004 4:16 PM
Subject: Re: [APML] Question about SCT and Giant Eazy Guider


> Hi Philip,
>
> I had read your article before.  From your article and other
> people's pictures, I learned that the giant easy guider works
> fine on 35mm cameras.  This makes me wonder if 35mm camera is
> its real limit and exactly how much I can get on a median-format
> film holder.
>
> I know that SCTs all have highly curved fields.  Does the
> Lumicon focal reducer also serve as field flattener?
>
> Thanks,
>
> Wei-Hao
>
>
> ______________________________________________________________________
> Wei-Hao Wang  :)
>
> Institute for Astronomy at University of Hawaii
>
> Address:                       Phone: 808-956-9867
> 2680 Woodlawn Drive            Personal Website:
> Honolulu, HI 96822             http://www.ifa.hawaii.edu/~wang
> ______________________________________________________________________
>
>
>
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> Astro-Photo mailing list
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> http://seds.org/mailman/listinfo/astro-photo
>

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