Physics

Telescope Field of View Calculator

Find the true field of view through a telescope.

Calculated Output

True field of view (°) 1.25

Formula: true FOV = apparent FOV ÷ magnification

Step-by-Step Breakdown

1. Values used:

2. Eyepiece apparent FOV = 50 °

3. Magnification = 40 ×

5. True field of view = Eyepiece apparent FOV / Magnification = 50 / 40 = 1.25°

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The math behind it

true FOV = eyepiece apparent FOV ÷ magnification. Higher magnification shrinks the view.

50° eyepiece at 40× → 1.25° true field.

Why does the Moon barely fit?

The Moon spans about 0.5°, so high magnification fills the view quickly.