Re: [ATM] 32" Focal ratio

[Aplanatic@aol.com]

Hi Scott,
 
I optimized a simple two-element coma corrector for a 32" f/5 parboloid and  
obtained very acceptable results at the corner of a KAF 1001 CCD.  The RMS  
spot size was a tad under 10 microns.  This suggests that an f/5 mirror  (1.2 
arcsec/pixel) can be reasonably well corrected for coma with a very simple  coma 
corrector.  I'd guess that a Paracorr would do somewhat better  yet.
 
Figuring and testing a 32" f/5 mirror is a big job and will require a  good 
optician to do the work.  Nonetheless, well within the  capabilities of a 
professional optician.  Mounting the beast is another  problem entirely.
 
I see no reason not to pick your favorite focal ratio between f/4.5 and  f/8. 
 The one thing I did not check was distortion, which may need to be  
corrected digitally during the process of making mosaics.
 
Best wishes on this wonderful project,
 
-- Dave
 
 
 
 
 
In a message dated 8/1/2005 5:17:30 P.M. Pacific Daylight Time,  
polaraligned@optonline.net writes:

> Hi  Scott,
>
> What is the largest camera you will be using with the  scope?  Are you 
> figuring the mirror or is someone else?   Will you be buying (or making) a 
> focal reducer?  How picky are  you about the images at the edge of the 
> field?  Do you plan on  doing mosaics?
>


Probably a KAF 1001 with a 24.6 x 24.6 mm  size.  24 um pixels.  It's
pixel size is a good match for the  long focal legnth without binning.
Plan on having someone else make  mirror.... Buying a coma corrector....
Well, of course I would like the  best possible images to the edge of field,
and I can't rule out  mosaics.  Am I asking too much?  How will this scope
compare to  an RC?  Oh, and the original question: Is a longer f ratio going
to  help me achieve better images, even with a corrector?

Opinions  appreciated,

Scott




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