Use this simple Excel spreadsheet to compare the magnification, FOV and exit pupil of various eyepieces as they would perform on your telescope.

You simply enter your telescopes objective diameter, focal length and the multiplier of any Barlow lens/focal reducer you use as well as the focal length and apparent field of view of up to 49 eyepieces you are looking at. The spreadsheet will calculate your telescopes f/Ratio, resolving limit, limiting magnitude, maximum FOV and magnification at prime focus as well as each eyepieces actual FOV, magnification, magnification per inch of apeture and exit pupil both with and without your Barlow lens. Some suggested eyepiece focal lengths will also be calculated for your particular telescope.

The spreadsheet comes pre loaded with data for Siebert 1.25" and GTO Plossl eyepieces.

Click here to download.