Re: ATM Astrographs

[Krajci Tom Capt Det 5 <krajci.tom@barksdale.af.mil>]

From: "Wagner,Rick [NCR]" <Rick.Wagner2@ec.gc.ca>

>Tom Krajci:
>I am just getting thru a few old ATM-list digests which I was unable to
read
>over my holidays and found your mention of your 6"/3.75 astrograph.  Is it
a
>home-made job?  If so can you describe to us the optical configuration,
>design etc.  

See these old posts from the archive for more info:  
http://www.system.missouri.edu/ics/staff/andy/ATM/ARCHIVES/NOV96/msg00237.ht
ml
http://www.system.missouri.edu/ics/staff/andy/ATM/ARCHIVES/SEP97/msg00123.ht
ml
http://www.system.missouri.edu/ics/staff/andy/ATM/ARCHIVES/FEB98/msg00045.ht
ml

Also, the six inch mirror has an eccentricity of 1.34. . .that seemed best
to match the Lumicon Comna Corrector I use with it.  As an astrograph it has
a large secondary - 2.6 inches!  I use a Taurus camera body with custom made
cell to hold the coma corrector at the correct spacing from the film plane.

>I have been figuring a 10"/3.5 sphere intending to try it out
>as a Waineo null, but then working it into a hyperbolic astrograph.  I
>started playing around with optical design software (KDP) at one point and
>wasn't getting anywhere fast enough to justify spending a whole lot of time
>on it then (other scopes to build and a family to support and tend to, you
>know the kind of thing).  I would be interested to know what you, or others
>who have developed such systems, did.

I reverse engineered the  Lumicon Coma Corrector and plugged that into ray
trace software.  The only variables I could then play with were main mirror
eccentricity and spacing of corrector lens to film plane.

See 
http://www.system.missouri.edu/ics/staff/andy/ATM/ARCHIVES/NOV96/msg00361.ht
ml for details on the Lumicon corrector.

Offhand I'd say an eccentricity of about 1.2 is a good starting point for
your ray trace analysis.

I recommend you use subdiameter laps to get the hyperboloid figure.

Hmmmm, Peter John Smith would probably be a big help in the optical
design/analysis department!

Hope this helps,
Tom Krajci