TEC: The Eyepiece Calculator

Copyright, © 2008, by David Paul Green, Los Angeles, California

Focal Length of Your Scope in millimeters (FLs)
Aperture of Scope in Inches (APi)
If you know the aperture of your scope in inches, enter it to the left. If you know it in mm, enter it to the right.
Aperture of Scope in mm (APm)

Barlow Power

(Enter Barlow Magnification)

Eyepiece Type/Description
(replace with your own)
Eyepiece Focal Length (FLe)
Eyepiece Apparent Field of View (FOV) °
Exit Pupil
(EX=APm/M)
Eyepiece
Power
(M=FLs/FLe)
Eyepiece True Field of View ° (T=FOV/M)
Barlow Factor
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.

Click to see apparent fields of view for common eyepieces:

Copyright 2008 by David Paul Green (used by permission)
Visit his website for more great free software