Telescope calculator
Match telescope and eyepiece to calculate magnification, exit pupil, and approximate field of view.
Your experiment
How it works
Magnification depends on both telescope and eyepiece. Exit pupil describes the diameter of the light beam leaving the eyepiece. A wider true field lets you see more of the sky at once.
Read the field note ↗About this model
True field ≈ apparent field / magnification. Dawes’ limit estimates resolution for double stars; atmosphere, optics, and target contrast affect actual results. Never view the Sun without a purpose-built front-mounted solar filter.
Telescope calculator: common questions
Is higher magnification always better?
No. High power can make a view dimmer and amplify atmospheric blur. Aperture and observing conditions matter.
What does exit pupil mean?
It is the width of the light beam leaving the eyepiece, equal to aperture divided by magnification.
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