Usable Magnification...

[mikeDnight]

That's a great paper John! I remember looking at some of the eyepieces at the Herschel museum and was amazed by just how tiny the eye lens was. Some looked no larger than the diameter of a hypodermic needle. I'd love to play with them under the stars!  Only a couple of weeks ago I used 1000X while examining a close double star. It was surprisingly comfortable with a field that seemed quite wide, but I think at that power the ragged edge of my iris became noticeable. The image still remained sharp though!