Re: ATM Opinions on Maximum Magnification vs: Seeing ?

[andydtg@alpha1.phoenix.net]

Tom Cathey wrote:

>For example, I find  229X, (20mm Nagler II,  22" F8.5) is the maximum I can
>run most any night. I've yet to find a night (except for viewing the moon at
>300X-400X) where I can go above 285X where images are not distorted.
>
>Another reason I would like to hear opinions here is because I suspect my
>optics to have about 1/3 wave spherical abberation  based on star tests from
>Suiter's book. Perhaps this ~ 229X magnification level is the point where it
>begins to show up??...or is it the seeing threshold?? It seems above 229X or
>so I see a combination of boiling and distortion, but I'm not sure.  Should I
>be happy at 229X enjoying reasonable images?

You have to use approx 13.3x / inch of aperture to enlarge the Airy disk (in
excellent seeing)to be large enough to be resolved by the eye with its approx
60 arc sec capability. For a 22" this is 293x. If you can see a disk at less x
it's bad seeing or bad optics or both.

Andy Saulietis / DTG Alt-Az-Fp Drive Systems
12617 Harriet Ln
Santa Fe, TX 77510 USA
409-925-8854 Voice/Fax