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Re: [APML] Question about SCT and Giant Eazy Guider
Hi Wei-Hao,
I haven't tried the GEG with a medium format camera but I think that the
area of the light cone would be far too small. With the 3-1/4" - 2"
adapter removed, the available light cone from an SCT is a little under 2"
in diameter. The GEG (uniquely amongst OAGs) allows the full light cone to
be used, however that is still far too small to cover medium format, which
would require an unvignetted light cone of at least 3" in diameter --
scopes dedicated to medium format provided a 4" unvignetted light
cone. Even if the light cone covered this area, the aberrations towards
the edge of field would be colossal (both coma and field curvature).
The Lumicon focal reducer doesn't serve as a field flattener - it's just a
simple focal reducer. The GEG design was really dedicated to 35mm film
only - making it work with larger formats could involve some pretty
extensive modification.
--Philip
At 04:16 20/06/2004 -1000, you wrote:
>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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Philip Perkins
<pgp@astrocruise.com>
Wiltshire UK & Luberon France
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