Quote:
Originally Posted by ghsmith45
Yes, it's quite easy to check if the mirror is bad--turned edge, rough surface, zones etc. However, with focal ratios of f5 and faster, testing to see if the mirror is good (ie how close the mirror is to a perfect paraboloid) is quite tricky if you haven't ever done it before. The star test is probably your best bet. See "Star Testing Astronomical Telescopes" by H R Suiter. Bintel sell it for $69--it's well worth the price.
Geoff
|
Getting Suiter's book is excellent advice. Using it I was able in about 10 min to show that an apo refractor I had sent to me was below par with undercorrection as well as astigmatism. Scope replaced with one that was near perfect. Easy to see once you know the signs (and you buy from a good retailer).