Re: ATM 11.2" F/2 Primary testing questions :)

[Aplanatic@aol.com]

Ken wrote:

> Did you forget that you can also do a double pass 
> autocollimation test with a flat?

Quite right, Ken.  I've never been able to get my hands on a high quality flat of this size, but if James can find one, then that's probably the best approach of all.  If I had a year or two to work on it, I'd try to make a 12" flat myself.  <g>  I think it's much easier to figure a 12" f/6 or f/8 paraboloid to 1/10th wave than to make a flat of this size to a similar accuracy.  That's why I use the secondary collimation telelscope technique.  But, if you happen to have a good flat just laying around...

Dave Rowe