RE: coma, coma, coma
DAVE MCCARTER (50VE3GSO@qstar.fanshawec.on.ca)
Mon, 1 May 1995 14:27:40 -0400 (EDT)
Coma is a result of the light rays being off the optical axis. We all know
(we do don't we? ) that a parabola reflects all parallel light on the
optical axis to a small point. However, as soon as the light beam is off
the axis, the
light is scattered across a wierd section, which is comatic.
Nagler and Lumicon I think have coma correctors which can squeeze the light
back into reasonably tight dots, but they are expensive esp in 2 inch.
Which is why the pretoria eyepiece was invented. see previous message. no
longer available, and most owners wouldn't sell theirs.
Was there ever an article in ATM on making a coma corrector?
Skies are still cloudy. Gonna grind glass.
Dave