Thanks,
Tony
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When replying, please replace NOSPAM with RANGER in E-Mail address.
It's a telescope specially designed for astrophotography -- not all that
common. The main desiderata would be: ability to focus with a camera body
attached in place of the eyepiece (some Newtonians won't); uniform coverage
of a 35mm film frame, or in many cases something larger; and color
correction suitable for photography (which nowadays mainly means you can't
get away with as much error in the deep violet as you can in a visual
instrument).
--
Clear skies,
Michael A. Covington / AI Center / The University of Georgia
Author, ASTROPHOTOGRAPHY FOR THE AMATEUR
http://www.CovingtonInnovations.com/astro <><
Hi Tony.
An astrograph is a 'scope designed specifically for astrophotography.
Depending on the design, some astrographs are not very suitable for visual
observing. For instance, in order to make a newtonian reflector better for
photography, you generally have to use a larger than normal secondary mirror
which increases the central obstruction. It affects contrast for visual
use, but will have a larger fully illuminated field to fill the frame on
film. There is usually some sort of trade-off involved.
Phillip
"Phillip" <jph...@charter.net> wrote in message
news:sn7fi2s...@corp.supernews.com...
The idea is to provide even illumination across a film-frame-size flat
field at fast f/ratio, without color shift and other optical problems.
This is difficult and expensive to do. None of these things is as
important for visual observing as for photo use. Film is very
unforgiving. The term "astro-graph" implies that the instrument is
designed for photographic purpose as much or more than for visual use.
In article <8l0bkv$ffo$1...@nntp9.atl.mindspring.net>,
"Tony" <NOS...@crosswinds.net> wrote:
> Technically, just what is an "astrograph" scope? How is it different
from
> other telescopes or just a fast visual tube ? Hope this isn't too
stupid a
> question, but I'm seeing the term used a lot and not sure why...
>
> Thanks,
>
> Tony
>
> --
>
> When replying, please replace NOSPAM with RANGER in E-Mail address.
>
>
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Before you buy.
Tony
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When replying, please replace NOSPAM with RANGER in E-Mail address.
<fros...@my-deja.com> wrote in message news:8l221t$vcm$1...@nnrp1.deja.com...