Telescope Calculator

Calculate telescope with Calculator 360 using the available inputs.

Telescope aperture diameter (mm)

Telescope focal length (mm)

Eyepiece focal length (mm)

Eyepiece apparent field of view (°)

Barlow or reducer factor (1 = none)

Wavelength for Rayleigh limit (nm)

Sensor width (mm, optional) For sensor calculations, enter width, height, and pixel size together.

Sensor height (mm, optional)

Pixel size (µm, optional)

Try an example

Open the available calculator.

Open the available calculator.

Calculate magnification, focal ratio, exit pupil, field of view, and optional sensor geometry from telescope specifications.

Enter the values required by the selected mode. Results use the shared calculator engine and its stated limits.

Local calculation; consult the method and limits shown below. References: Sky & Telescope eyepiece optics · Sky & Telescope field and exit pupil ·

What does this tool calculate?

Calculate magnification, focal ratio, exit pupil, field of view, and optional sensor geometry from telescope specifications.

Are the results estimates?

Check the assumptions and limits shown for the selected calculation.