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RE: Mosby Null Test

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Posted by Stephen Campbell on March 15, 2000 10:33:15 UTC

The mobsby null test is an inverse grating,alot like the ronchi test, which is
used to locate the 70% zone of a moderate to long focal length mirror,i used this test
once with a 4.25" f/12,but ended up leaving it spherical,because a mirror that diameter
and f-ratio is diffraction limited when left spherical,you can order a mobsby null test for
mirrors from 4.25" to 12.5" for around 10 bucks from willmann bell.
I know a guy here in tucson who would be perfect for writing an article about testing mirrors
his name is Bob Goff,he has a company called Astronomically Xenogenic Enterprises(A.X.E*) This guy
is probably one of the best(if not THE best)opticians in the world. he makes better that 1/100 wave
optics(no kidding!)alot of amateurs claim to have achieved 1/20,1/30 wave,but alot of them use the
couder mask method,you dont see enough of the subtle details that are between the openings of the mask
to achieve this level of perfection,its time alot of people learn a superior method of testing
bob goff email: goffaxe@azstarnet.com
hope this answered your question....stevec

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