Re: [ATM] [atm] how to test flat secondary mirror

["Bob May" <rmay@nethere.com>]

First off, please start using the caps key on your keyboard
correctly.  English usage of upper case only on the characters of
the language is considered very rude and is called "shouting".
It's like having a guy stand right by your ear and shouting into
your ear.  Same thing only visually.

Flats are usefull for all kinds of things Small ones in a
telescope are useful for changing the direction of the light beam
in any telescope.  Cassegrains find them useful when the builder
doesn't want to put a hole in the center of the primary mirror as
you both get rid of that problem and also allow the EP to bbe
placed at the side of the scope.
In larger sizes, it makes for a much more sensitive version of
the Foucault test to be done as the tested mirror is tested at
the focal length of a parabola and thus the test becomes a test
for a flat field like testing a sphere at it's ROC.

Bob May
Due to the large volume of SPAM thaat I'm getting, add an open
square bracket to the subject line or my spam filter will reject
your post~
rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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