Re: ATM Unobstructed Optics Viewing

[andydtg@alpha1.phoenix.net]

Bratislav wrote:

>there is NO 20" APO in
>existance, and even 12" ones are difficult/impossible to get. 

I think there's a 4 element 28" aperture apo in the Sunspot
vertical tower telescope. Probably not usable off vertical
due to gravity deformation of the glass.

Re off-axis masks, I agree they don't improve the performance
of a really good mirror. However I've used a 9" mask with my
24"f4 and a 13" mask with the 32"f4 in mediocre seeing and gotten
images better than at full aperture. I did a series of CCD 
images of the Comet S-L Jupiter spots with the 24" & had to
use the 9" mask because of poor seeing most of the time.

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