Re: ATM Diagonal size for CCD-only scopes?

[astroguy67@attbi.com]

Dave,

One other consideration, with such a fast system, focus 
will be very critical.  You should plan to have a 
well-crafted focuser capable of very small incremental 
adjustments.

-Jim McKay
> 
> Dave,
> 
> You will need to make sure the focal plane is accessible within the imaging 
> device.  It would be helpful for you to know the distance from the secondary 
> to the CCD at the most-racked-in position.  Actually 2" doesn't seem to big 
> to me, especially for such a fast scope.
> 
> Good luck,
> Shane LaPierre
> 
> 
> >From: Dave Strout <dstrout@linuxfoundary.com>
> >Reply-To: Dave Strout <dstrout@linuxfoundary.com>
> >To: atm@shore.net
> >Subject: ATM Diagonal size for CCD-only scopes?
> >Date: Thu, 26 Sep 2002 09:52:00 -0400
> >
> >
> >How does one go about sizing the diagonal for a scope whose only functions 
> >is to host a CCD camera at prime focus?  I've been thinking that you could 
> >go with a much smaller diagonal, since the CCD is typically small (around 
> >1/2" or so), but what is the calulation?
> >
> >The formula I've seen on the ATM calc site is:
> >w=d(D-a)/f +a
> >
> >with:
> >d = f.p. to diagonal
> >D = primary diamter
> >a = size of f.p.
> >f = focal length
> >w = diagonal width
> >
> >For my 8" F3.6, with a =1/2", and 2" backfocus (i.e. d = 6), I get a 2" 
> >diagonal.  That seems pretty big to illuminate a 1/2" CCD.  So, what am I 
> >missing?  I could get it down to 1.5" if I put the f.p at the tube wall....
> >
> >thanks,
> >dave.
> 
> 
> 
> 
> _________________________________________________________________
> Send and receive Hotmail on your mobile device: http://mobile.msn.com
> 
>