[ATM] 8" Diagonal- More info

[Polaraligned <polaraligned@optonline.net>]

Mark,

I plan on using the scope visually on occasion.  If not,
I would put the camera on the primary's axis without 
a secondary.  I know 8" produces a fully illuminated 
field a lot larger than I need, but I see no great advantage
to being able to swap in a smaller diagonal.  If I use 
the same Wynne corrector for visual use, it needs a 
ton of backfocus from the telescope.  I  just don't see
dropping the CO from an 8" diag to a 6" diag as being
that big of a deal, I would rather just keep the 8" as 
tight of a profile as I can and keep it a good quality
especially in the center.  As I said originally, it's quality
it going to fall off towards the edges.

So any opinions out there as to thickness?  or support
points?  Or should I just "wing" it because it does not
matter.

Scott



> Date: Mon, 26 Dec 2005 14:27:56 -0500
> From: Mark Holm <mdholm@telerama.com>
> Subject: Re: [ATM] 8" Diagonal- More info
> 
> Pardon me for being blunt, but why the emphasis on surface accuracy for
> an instrument to be used at prime focus with a ccd camera?  Your
> resolution is going to be nowhere near diffraction limited, instead, it
> will be pixel size limited.  I'll bet, a calculation would show you can
> tolerate wavefront errors that would horrify a planetary or double star
> observer and still produce ccd images not even measureably below
> "perfect" quality.
> 
> Maybe save some money by putting looser specs on that huge diagonal and
> put the money into a quick change arrangement on the secondary mount, so
> you can switch to a smaller, higher quality diagonal for visual use.
> 
> Mark Holm
> mdholm@teerama.com
> 

_______________________________________________
ATM mailing list http://www.atmlist.net/