Calculate astrophotography pixel scale (arcsec/pixel), sensor field of view, and sampling assessment for your setup.
Enter your camera's pixel size in microns, the imaging focal length in millimeters, the sensor resolution in pixels, and your typical seeing in arcseconds. Pixel scale is 206.265 × pixel size ÷ focal length.
For example, 3.76μm pixels behind a 530mm telescope give 206.265 × 3.76 / 530 ≈ 1.46 arcseconds per pixel, and multiplying by the pixel count along each axis (then dividing by 3600) yields the sensor's sky coverage in degrees.
The sampling verdict uses the Nyquist guideline of half your seeing: with 2.5-arcsecond seeing the ideal scale is 1.25 arcsec/pixel. Scales below half that ideal are flagged as oversampled, while scales more than 1.5 times the ideal count as undersampled.
One radian contains 206,265 arcseconds. Because pixel size is entered in microns and focal length in millimeters, a factor of 1,000 cancels, leaving pixel scale = 206.265 × pixel size ÷ focal length in arcseconds per pixel.
Oversampling spreads a star across more pixels than the seeing justifies, costing sensitivity; undersampling renders stars blocky and discards detail. This calculator flags scales finer than half the Nyquist target as oversampled and coarser than 1.5 times it as undersampled.
A common guideline is half your typical seeing — the Nyquist-style target used here. With 2.5-arcsecond seeing, aim near 1.25 arcsec/pixel; anything between roughly 0.6 and 1.9 arcsec/pixel still falls inside the optimal band for that seeing.
Multiply the pixel scale by the sensor's pixel count along each axis, then divide by 3,600 to convert arcseconds to degrees. A 1.46 arcsec/pixel scale on a 6248 × 4176 sensor covers about 2.5° × 1.7° of sky.