Telescope magnification and field of view
Compare an eyepiece with your telescope. See magnification, approximate sky coverage and exit pupil together.
Your inputs
Start with the example values, then replace them with your own. For tables, keep the vertical bar separators and use a dot for decimals.
Never look at the Sun through a telescope or binoculars without correctly fitted specialist solar equipment. These calculations do not establish safe equipment use.
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Result and workspace
Use the start button to open your result or activity.
How it works
Magnification = telescope focal length / eyepiece focal length. Approximate true field = apparent field / magnification. Exit pupil = aperture / magnification. Distortion and field stops can change actual coverage.
Worked example
These sample results use the original example inputs in the form. They do not change when you edit your inputs; your own result appears in the workspace.
- Magnification: 40 ×
- Approximate true field: 1.25 degrees
- Exit pupil: 2.5 mm
Read the result carefully
Results depend on the values and assumptions shown above. Change one input at a time to see its effect. A blank or unavailable result means the data does not support a calculation; it is not zero.