Telescope Field of View Calculator

TFOV = AFOV / Magnification

Eyepiece Apparent FOV (degrees)

Objective Focal Length (mm)

Eyepiece Focal Length (mm)

Formula

True FOV = Apparent FOV / Magnification

What is true field of view?

The actual angular extent of sky visible through the telescope. It equals the eyepiece apparent FOV divided by magnification.

What is a good field of view?

Wide-field eyepieces (60-82 degree AFOV) give larger true fields. Lower magnification also gives wider fields.

Free telescope magnification calculator. Calculate the magnification power of a telescope from focal length and eyepiece.

Free telescope aperture calculator. Calculate resolving power and limiting magnitude from aperture.

Free angular diameter calculator. Calculate the apparent angular size of an object given its physical size and distance.