This calculation takes a few simple rules on eyepieces and telescope
or system magnification, and outputs a table of magnification or
"powers" for a given telescope or optical combination.
Telescope magnification is telescope (or system) focal length
divided by eyepiece focal length -- a telescope with a focal length
will give a magnification of 200x with a 10mm eyepiece. Another
good rule is: don't try to force more than 50x-60x magnification
per inch of aperture. For an 8-inch telescope, this would put 400-480
as the upper limits for magnification.