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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 white or dark red boxes. Do not exceed the maximum number of characters, delete characters if necessary.

You use the information on your own risk! There can always be a mistake in my equations behind the calculations, check that the result is correct. Let me know if you find something wrong and I try to correct it. Some calculations are very simple done and not correct in the small details.

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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