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Astronomy Calculations:
Field of view, exit pupil, magnification

With this tool you can find the field of view, the exit pupil and the magnification for a telescope or binocular. This is for visual observing.

When doing visual observations it could be interesting to know the telescope's or the binocular's output pupil, the eye's pupil diameter is about 6 mm in dark condition. No value to have a bigger size exit pupil than that from the telescope or binocular. You also get the f/stop and fov (field of view) seen through the ocular. Compare with Moon's 0.5o (half degree).


Type in your data

It start to calculate as soon you change or write new figures in the dark red boxes. Do not exceed the maximum number of characters, delete characters if necessary.

There can always be a mistake in my equations behind the calculations, I try to correct it as soon as I find it wrong.

Telescope focal length

Ocular focal length

= Calculated results
0 to 9999 mm 0 to 99 mm   Angle Magnification

Telescope opening diameter

= 0.0
0 to 999 mm f/stop
= 0.0
  exit pupil diameter

Ocular's apparent fov (field of view)

true field
= 00.0
0 to 90 degree degree
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