Eyepiece Power

Tables for Eyepiece Magnification

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 of 2000mm 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.

Usage: To get a table of magnifications for a specific telescope, select the telescope from the popup below. The program will output a list of magnifications for a range of popular eyepiece sizes. If you are interested in a particular eyepiece, select an optional eyepiece model and the program will highlight the row for that eyepiece, in blue. As usual, either enter the value(s) manually, or select from the popups.

(1a) select telescope:
(1b) (OR) enter telescope focal length:

Make	Model	f-ratio

(2a) eyepiece focal length (mm)
(2b)(OR) eyepiece focal length (mm)
(manual entry)

(popular models, pick by mm)
F2 by model
F2 by focal length

CREDITS: Move mouse pointer to see links.