On Wed, 22 Sep 2004 04:17:49 -0500, Jim Beam wrote:


I read different numbers for how much you can milk out of a specific aperture. I am considering a 7" APO.

Some people say 30x per inch, thats it for detail. Well, thats only 210x which seems conservative for a 7" APO.

Many people say 50x per inch, and thats 350x for a 7" APO, sounding better.

But on nights of superb seeing, how far can you take a superb 7" APO, like a TMB or an AP? Can you view Saturn at 500x? 600x? When does decreasing brightness become a problem, and when does additional detail fail to appear?

Thanks
JB

I bought a TMB115 earlier this year, and in initial tests used
magnifications of up to 335x on Jupiter and Saturn, though the image was
starting to get a bit dim (75x per inch). Generally I preferred to use
somewhat lower powers-say around 50 per inch, but bear in mind the scope
was not mounted equatorially at the time.
I would agree with others that the high end apos will take around 100x per
inch when conditions allow, which with something as big as a 7" is not
likely to be all that often unless you have an extremely good site.
Phil