Field of view
It gives the image’s angular width and height. A larger sensor covers more sky at the same focal length.
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How much sky fits
in your image?
One sensor, one focal length: discover the area of sky recorded and the angle covered by each pixel.
Your setup
Generic example: a 23.5 × 15.6 mm sensor, 3.9 µm pixels and a 750 mm focal length. Replace these with your equipment’s values.
Field of view & pixel scale
—Horizontal field of view
—Vertical field of view
—Arcseconds per pixel
—Effective focal length
The rectangle illustrates only the sensor’s proportions, without simulating a celestial object.
Results appear after calculation.
Reading these numbers
Pixel scale
It gives the angle covered by one pixel. This number alone does not measure the resolution actually achieved: optics, turbulence and tracking also play a role.
Effective focal length
It includes the reducer or Barlow factor. Use the actual factor of your setup when known.
Formulas, units and limitations
Effective focal length = focal length × optical factor.
Field of view (degrees) = 2 × arctan(sensor dimension ÷ (2 × effective focal length)) × 180 ÷ π.
Pixel scale (arcseconds/pixel) ≈ 206.265 × pixel size (µm) ÷ effective focal length (mm).
Geometric model for a prime-focus image, flat sensor and square pixels, without binning. Distortion, vignetting and eyepiece projection are not modelled. The pixel scale uses the small-angle approximation.
Educational reference on sensor–telescope field of view: Celestron — Field of view for a CCD chip and telescope, accessed on 18 October 2026. Local calculations; no equipment data are sent.