Free online tool

Telescope Field of View and Image Scale Calculator

Calculate camera field of view, image scale, magnification and exit pupil

Telescope and optics

Telescope focal length (mm)

Aperture (mm)

Reducer / Barlow factorExamples: 0.63× reducer, 1× native, 2× Barlow.

Eyepiece focal length (mm)

Eyepiece apparent field (degrees)

Camera

Pixel size (µm)

Width (pixels)

Height (pixels)

Sensor dimensions are derived from resolution × pixel size.

Effective focal length

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Focal ratio

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Image scale

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Camera field

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Sensor size

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Magnification

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Exit pupil

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Eyepiece true field

—

Optical resolution estimates

Sampling

Telescope image scale and field of view

Calculate the angular sky covered by a camera sensor, arcseconds per pixel, focal ratio and common visual-observing values. Camera field uses the exact rectilinear angle formula; image scale uses the standard small-angle constant of 206.265.

Dawes and Rayleigh limits describe ideal diffraction resolution. Atmospheric seeing, focus, tracking, optical quality, filters and processing normally determine the useful real-world sampling.