Re: ATM Combine Newton/MX916 CCD ?

[Anthony Stillman <atmer@flash.net>]

>...13,1" Newtonian. f4,5
>...1450mm...combin(e)...with CCD.
>... better to combine a Cassegrain with CCD

Timo,

Others can speak more athoritatively I'm sure.  However, this concern most
probably arises from sampling theory.  The short of it is you want the
sampling frequency to mate with the signal.  That is, in general you want
two or three pixels to subtend the idealized star image.  Cassegrains
generally are slower and have much longer focal lengths, hence larger image
scales and Airy disks.  This would make sense for a CCD with large pixels.
Somewhere I have several extensive write ups on matching detector arrays
with optical systems.  I think it is covered in Christian Buil's "CCD
Astronomy", but don't quote me.  Also, I vaguely recall an article in S&T.
I'll poke around for a reference or two.

I know I'm venturing into an area where others on this list are practiced
experts.  I hope said experts fell free to expound.

Anthony