2 arcsec seeing, 3.76 µm pixels, 480 mm
2 / 1.6157 = approximately 1.2378 pixels per entered seeing FWHM. The output is a numerical ratio, not a well-sampled purchasing certification.
Load this example in the calculatorSeeing and pixel-sampling calculator
Express an entered seeing FWHM in pixels using your camera pitch and effective focal length, without an automatic good/bad verdict.
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What this calculation tells you
Sampling combines two different quantities: angular image scale and an estimate of seeing width. Keep them separate. Changing a camera pixel size changes the sampling ratio; it does not improve atmospheric seeing.
Inputs and workflow
- Enter the telescope’s effective focal length and camera pixel pitch.
- Enter an angular seeing FWHM estimate in arcseconds, not a star width already measured in pixels.
- Read pixels per entered FWHM. Compare more than one plausible seeing value rather than treating a single estimate as a guarantee.
Formula and units
Pixels per FWHM = entered seeing FWHM (arcsec) / image scale (arcsec/pixel). Image scale = 206.264806 × pitch (µm) / focal length (mm).
Worked examples
4 arcsec seeing with the same equipment
4 / 1.6157 = approximately 2.4756 pixels per FWHM. The larger ratio describes a broader seeing width, not sharper stars.
Load this example in the calculatorLimits before using the result
A seeing-only estimate omits diffraction, focus, guiding and sensor response. Measured stellar FWHM can contain several of those effects and is not interchangeable with atmospheric seeing alone.
No universal under/over/well-sampled label is assigned. Camera purchasing also depends on field size, optical correction and the intended imaging workflow.
Sources and method notes
- Atik: image-scale calculation
Source for the pixel-size/focal-length conversion. Its ideal-scale purchasing thresholds are not adopted here.
Calculation notes maintained by AstroGearFit. Updated September 7, 2026. Examples are numerical demonstrations, not hands-on equipment tests. The method notes are currently in English; the existing interface language selector remains available.
Choose a calculation
Five focused checks with reproducible examples and explicit limits. These tools do not certify a complete equipment combination.
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Estimate rectangular camera field width and height from sensor dimensions and effective focal length.
- Pixel-scale calculator
Convert camera pixel pitch and telescope effective focal length to angular image scale in arcseconds per pixel.
- Seeing and pixel-sampling calculator
Express an entered seeing FWHM in pixels using your camera pitch and effective focal length, without an automatic good/bad verdict.
- Mount payload comparison calculator
Compare a declared carried mass with the manufacturer rating for the exact mount configuration and identify an excess explicitly.
Filter sizing is paused. Whole-system compatibility needs verified interfaces, optical specifications and configuration-specific evidence.