Quote:
Originally Posted by multiweb
That moon shot looks good. Very close to the finished product now.  |
Thanks Mark, and you are absolutely right about being close with the optics: With Bratislav's help, I did a couple more Roddier tests and it turns out that no figuring is required.
The first one was done a few days ago and the only change from the last posted Roddier test is that I rotated the Mangin about 90 degrees. Interestingly the orientation of the astigmatism remained the same, suggesting that the problem may not be the Mangin.
I was planning to do some more testing to isolate the problem and, last night, as a first thing to try, I slackened the retaining ring of the front lens, and Bingo!, the astigmatism was gone. See the second attached test result.
Bratislav reckons that it is as good as astrographs get.