Re: [APML] Coma corrector needed ?

["Tom & Lou Krajci" <krajcit@3lefties.com>]

From: "Mike & Dianna" <galaxy@ncweb.com>

> I have a home built 8" F3.5 newt for AP only . When I researched coma
> correctors, Lumicons and the TeleVue parracor, I found that the Lumicon
has
> a larger area of glass than the Televue....therefore less vingetting.

I disagree.  The spacing for the Lumicon corrector is farther from the film
plane than for the Televue corrector.  For an f/4 type of light cone...they
both should give roughly the same 100% illuminated field...about 1 inch in
diameter.  Because the Lumicon corrector is a bit farther (3 and a little
inches versus 2 and a little inches for TeleVue)...the rate of illumination
fall off for the Lumicon may be a bit less severe outside the one inch
diameter circle...but it's probably not a big difference.

Also, the TeleVue will give tighter star images if you plan to do visual
work with your scope at higher powers.  The Lumicon is corrected for photo
work only, and will show mushier images for visual work.

Tom Krajci


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