"David Neal Minnick" wrote in message
om...
Can someone draw me a word-picture or direct me to a resource showing
just how the focal length of an ep is measured? That is, if one could
cut an ep in half lengthwise showing everything intact, from which
part to which part is the f/l measured?

David Neal Minnick
Lake Elsinore, CA

"The meek shall inherit the gulag."

This website shows calculations for 2-3 element eyepieces:
http://www.astronomyboy.com/eyepieces/ep_calc.html

Regards,
Ed T.