AstroPrep

Preprocessor for nova.astrometry.net

Pick or capture a photo from your phone gallery. JPEG, PNG, HEIC supported.

Original

Output

idle
Estimated detections: 0 stars
Parameters

Detect the eyepiece field by luminance, crop to a square and mask the boundary to eliminate noise. 1 = on (default), 0 = off (process full frame).

×

Process at 1/N resolution. Higher = faster, lower memory. Default 2× is good for 12 MP iPhone shots.

px

Median filter size for sky-glow estimation. Default 20.

DN

DN above local background to enter detection. Default 20.

px

Real stars are large diffuse blobs, noise spikes are tiny. Default 4.

px

Discard very large blobs (clouds, glow, lens-flare). Default 2000.

Peak/area ratio. Real stars ≤ 6.0, noise spikes ≥ 10. Default 6.0.

RGB coefficient of variation. Stars are neutral white; ISO noise is coloured. Default 0.5. Set to 1.0 to disable.

Gaussian profile sigma for accepted stars. Default 1.5 — smooths centroids for the source extractor. Set to 0 to disable.

×

Brightness multiplier after normalisation. Default 3.0 — keeps faint stars visible without saturating the bright ones.

DN

Output background grey level. Default 12 — small lift helps astrometry's source extractor pick its detection threshold.

Log