From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


As to the dubiousness of startesting, I'll note Peter Ceravolo's 4 scopes
with the calibrated amount of error in them.  The difference between the
1/8th and 1/16th errors ended up being visible only to experienced
observers and only on a rare day when the sky was sufficiently stable to
allow the use of such a fine mirror.
As such, anything over that 1/8th wave mirror is pretty much not visible in
the star test, negating the possibility of finding errors much finer than
that level of accuracy.  This puts the star test in the regime of tests to
find more crude error levels than a good Foucault or even a Ronchi test,
either at the sky or on the bench.  Not what I'd call good for the levels
of accuracy that are often attained by many of us in making a mirror. Thus,
the star test will tell us if we are close to a usable scope but won't tell
us how close to perfect.
Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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