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

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

See myu webpages for an article on doing flats.  You end up with
one good flat at the minimum and two lesser quality flats if you
don't wish to finish those two off.
If you really want to impress your friends, make some larger
flats so that you can autocolikate your scope.  Large flats are
always quite useful and one of those great uses is as the
steering mirror for a solar disk display.  Put the flat on a  sun
tracking axle and direct the light to a very long focal lentth
spherical (good enough for vvery ling focal lengths_ and shine
that on a wall.  It is an inch of diameter per about a hundrred
and fifteen inches of focal lentth so figure accordingly. Fine
tracking can be done by the mere exedient of putting two
photocells on either side of the sun's image and letting the sun
stay between them You can alsoi do a elevation control for daily
or weekly correction of the sun's vertical position in tyhee same
way.
Bob May
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