[ATM] Figuring a Schmidt Corrector

["Shekhar Phatak" <shekhar@vsnl.com>]

Hello all,

 

I have recently made a 12" f/4 Newtonian as my first project (thanks to the
ATM archives) and it is functioning beautifully. It however suffers from
coma off axis which is quite bad for bright objects such as planets. Is
there any corrector available for this problem? Could you give the necessary
links?

 

Secondly, I am planning to make a 12" SCT (primary f/1.5) with an aim to do
astrophotography starting the next season (November 2004). We have
fortunately excellent skies November to April and I would like to take
advantage of the same. I have all the material ready except information on
figuring a Schmidt plate. I do not want to use the vacuum pan method since I
lack the technical resources to make the pan. Recently I came across an
article (ATM3, H.W. Cox and L. A. Cox) describing a method of making Schmidt
plate using petal lap. The article is however silent on the kinds of strokes
to be used. I live in Pune, India and there not many adventurous amateur
telescope makers around who could help me. My question is:

 

1.	What should be the exact shape of the petals?
2.	What kind of strokes should be used to make a Schmidt plate using
this method?
3.	Is there any other method of making a Schmidt plate other than the
vacuum method?
4.	If yes, where could I find information on them (links etc.)
5.	If no, could anyone suggest to me any other design, which I could
use for astrophotography? 

 

Thanks in advance,

 

Shekhar Phatak

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