astropywcs

Astropy.wcs is a subpackage of the Astropy project that provides tools for handling the World Coordinate System (WCS) information used in astronomical images. It enables the mapping between pixel coordinates in an image and celestial coordinates on the sky, based on the WCS metadata commonly stored in FITS headers.

The module can construct a WCS object from a FITS header and extract key information such as the projection type (CTYPE), reference coordinates (CRVAL), reference pixel (CRPIX), pixel scale (CDELT) or distortion matrices (PC or CD), and any other WCS terms. It supports multi-dimensional WCS definitions, various celestial reference frames (e.g., ICRS, FK5), and standard projections like TAN and SIN. Transformations are provided in two directions: pixel-to-world (wcs_pix2world) and world-to-pixel (wcs_world2pix), returning coordinates in physically meaningful units when available. The library also integrates with astropy.coordinates for conversions to standard coordinate frames and with astropy.io.fits for reading and writing headers.

Typical use cases include astrometric calibration, image re-projection, and coordination of image data with other datasets. It interoperates with other Astropy components such as WCSAxes for visualization and coordinates for downstream calculations. The package focuses on standard, widely used WCS representations and is designed to work smoothly within the broader Astropy ecosystem, though highly non-standard or severely distorted WCS definitions may require additional tooling or custom handling.

See also: FITS, World Coordinate System, astropy.coordinates, astropy.io.fits, WCSAxes, astropy.wcs.