SExtractor
SExtractor (Source Extractor) is a tool for detecting and measuring sources (stars, galaxies, and other astronomical objects) in images. It generates catalogs with positions, fluxes, and morphological parameters.Input formats
.fits, .fit, .png, .jpg, .jpeg, .tiff
Parameters
| Parameter | Range | Default | Description |
|---|---|---|---|
| Detection threshold | 0.1–100 sigma | 1.5 | Minimum significance above background for detection |
| Minimum area | 1–1000 pixels | 5 | Minimum connected pixel area for a source |
| Deblending sub-thresholds | 1–128 | 32 | Number of thresholds for deblending overlapping sources |
| Deblending min contrast | 0–1 | 0.005 | Minimum contrast for deblending |
| Catalog format | JSON / CSV | JSON | Output catalog format |
Outputs
| Output | Format | Description |
|---|---|---|
| Source catalog | JSON or CSV | Positions (RA/Dec or pixel), fluxes, magnitudes, morphology |
| Overlay image | PNG | Original image with detected sources marked (optional) |
Presets
| Preset | Description |
|---|---|
| High Sensitivity | Lower threshold, detects fainter sources |
| Conservative | Higher threshold, fewer false positives |
Compute requirements
| Resource | Requirement |
|---|---|
| GPU | None — CPU only |
| Duration | ~20 seconds per image |
Catalog fields
The output catalog includes:- Position — X, Y pixel coordinates (and RA/Dec if WCS is available)
- Flux — integrated flux and peak flux
- Magnitude — instrumental magnitude
- Shape — ellipticity, position angle, FWHM
- Flags — quality flags for each detection