Expected HFR Matrix

Predicted NINA-style HFR in pixels for each telescope and sensor, from seeing, diffraction, guiding and pixel size. Tap a cell for the full breakdown.

Seeing (FWHM)

2.5″

Typical conditions

Forecast for a US ZIP code

Guiding RMS (total)

0.50″

Filter

HFR definition

Binning

Undersampled (FWHM < 2 px) Well sampled (2–5 px) Oversampled (> 5 px) Big number = HFR px · small = FWHM px · MP in each column header updates with binning

Your equipment

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Brands

Manufacturer focal lengths, plus the matching reducer or flattener where one is sold. Entries marked ≈ are aperture × focal ratio where the maker doesn't publish a focal length. Plate-solve your own rig for exact numbers.

Telescopes

Cameras

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Cameras by sensor

Sensor	Pixel	ZWO	Player One
IMX183	2.40 µm	ASI183MM Pro, ASI183MC Pro	No model
IMX492 (294 mono)	4.63 µm bin2 2.315 µm bin1	ASI294MM Pro	Artemis-M Pro
IMX294 (294 color)	4.63 µm	ASI294MC Pro	Artemis-C Pro
IMX571 (2600)	3.76 µm	ASI2600MM Pro, ASI2600MC Pro (and Duo/Air)	Poseidon-M Pro, Poseidon-C Pro
IMX410 (2400)	5.94 µm	ASI2400MC Pro (color only)	No model
IMX455 (6200)	3.76 µm	ASI6200MM Pro, ASI6200MC Pro	Zeus 455M Pro, Zeus 455C Pro
IMX585	2.90 µm	ASI585MM Pro, ASI585MC Pro	Uranus-M/C (Pro), Xena 585M

Model

scale″/px   = 206.265 × pixel_µm / focal_mm
diff″       = 1.03 × λ / D × 206265            (Airy FWHM, obstruction ignored)
guide″      = 2.355 × guiding_RMS              (RMS → FWHM)
pixel″      = 0.68 × scale                     (square-pixel blur, 2.355/√12)
FWHM″       = √(seeing² + diff² + guide² + pixel²)
HFR_true″   = FWHM / 2                         (Gaussian star)
HFR_NINA″   = 1.0645 × FWHM / 2                (flux-weighted mean radius)
HFR_px      = HFR″ / scale

Real stars run larger. Stars have Moffat-like wings, and background noise inflates a weighted-mean radius, so expect measured NINA HFR to come in somewhat above these values. Use the matrix for relative comparisons and sampling, not as a pass/fail target.
Color sensors match mono in this table. Behind a Bayer matrix each red or blue channel is sampled at twice the pixel pitch, so undersampled cells are worse in practice on MC/C cameras.
Fast optics aren't modeled. The RASA 8 (f/2) and Pleiades 68 (f/3.8) have real optical spot sizes and are very sensitive to tilt and backfocus, which typically adds blur beyond this model.
Correctors change focal length. Newtonian coma correctors and RC flatteners shift focal length a few percent, and GSO RC10s plate-solve anywhere from about 1950 to 2030 mm. Plate-solve your own rig and use that scale.
Binning: the Binning control multiplies every pixel size (IMX571 at 2×2 = 7.52 µm). On these CMOS cameras binning is done in software, so it changes sampling and per-pixel SNR but not read noise per binned pixel. The 294MM's default mode is already bin2 (4.63 µm), so its "IMX492 bin1" column at 2×2 matches the 4.63 µm column at 1×1.