Technique

Nyquist Sampling

Matching pixel size to telescope resolution for optimal detail capture

Definition

Nyquist sampling requires at least 2 pixels across the smallest resolvable detail (Airy disk). For planetary imaging, 2.5-3.5x sampling is optimal. FORMULA: Image scale (arcsec/pixel) = 206.265 × pixel_size(µm) / focal_length(mm). EXAMPLE: ASI462MC (2.9µm pixels) at 3000mm focal length = 0.20 arcsec/pixel. Dawes limit for 8" scope ≈ 0.57 arcsec, so this gives ~2.8x sampling (ideal). RULE OF THUMB: Optimal f-ratio ≈ 5 × pixel_size_in_µm. For 2.9µm pixels, target f/14-f/15. Under-sampling (f/8 with small pixels) loses resolution; over-sampling (f/30) wastes light.

Related Terms

Focal Ratio (f/number)

Telescope focal length divided by aperture diameter

Barlow Lens

Optical element that increases telescope magnification

Arcsecond

Angular measurement unit (1/3600 of a degree)

See It In Action

Learn how Nyquist Sampling is used in planetary imaging with our step-by-step guides:

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