CCD Pixel Scale Calculator
Pixel scale is how much sky one camera pixel covers through your telescope, measured in arcseconds per pixel. It follows a clean geometric relationship: 206.265 times the pixel size in microns divided by the telescope focal length in millimeters. A longer focal length or a smaller pixel gives a finer scale and a narrower field. This calculator returns the pixel scale and the full sensor field of view in both axes from your pixel size, focal length, and sensor pixel counts. Enter the effective binned pixel size if you image with binning; all inputs are your own equipment values.
Pixel scale formula
pixel scale = 206.265 * pixel size (um) / focal length (mm)
field width (arcsec) = pixel scale * width in pixels
field width (arcmin) = field width arcsec / 60
field width (degrees) = field width arcmin / 60
The constant 206.265 converts microns per millimeter into arcseconds, since one radian is 206,265 arcseconds. Multiply the scale by the pixel count on each axis for the field of view.
Imaging scale notes
- Around 1 to 2 arcseconds per pixel suits typical deep-sky seeing.
- Longer focal length gives a finer scale and a narrower field.
- Binning two-by-two doubles the effective pixel size and the scale.
- Oversampling wastes detail; undersampling loses resolution.
- Use the published pixel size and sensor dimensions for your camera.
Pixel scale: frequently asked questions
What is pixel scale?
Pixel scale is the angle of sky covered by one pixel of your camera through a given telescope, in arcseconds per pixel. It equals 206.265 times the pixel size in microns divided by the focal length in millimeters. It determines how finely your image samples the sky.
What pixel scale should I aim for?
A common guideline for deep-sky imaging is roughly 1 to 2 arcseconds per pixel to match typical seeing. Much finer (oversampled) wastes detail to noise, and much coarser (undersampled) loses resolution. The ideal depends on your seeing, so treat this as guidance.
Where do the 206.265 come from?
It is the number of arcseconds in one radian divided by 1,000. One radian is 206,265 arcseconds, and since pixel size is in microns and focal length in millimeters, the unit conversion leaves the factor 206.265. It is a fixed geometric constant, not an estimate.
How does focal length change the field of view?
A longer focal length gives a smaller pixel scale, so each pixel sees less sky and the overall field is narrower but more magnified. A shorter focal length spreads more sky across each pixel for a wider field. The calculator also returns the full sensor field of view.
Does binning change the pixel scale?
Yes. Binning combines pixels, so two-by-two binning doubles the effective pixel size and therefore doubles the pixel scale. Enter the effective binned pixel size if you image with binning to get the correct scale.
Official sources
- NASA Imagine the Universe: detectors and imaging.
- NASA Science: how telescope cameras work.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.