celestial_frame_to_wcs

astropy.wcs.utils.celestial_frame_to_wcs(frame, projection='TAN')[source]

For a given coordinate frame, return the corresponding WCS object.

Note that the returned WCS object has only the elements corresponding to coordinate frames set (e.g. ctype, equinox, radesys).

Parameters
frameBaseCoordinateFrame subclass instance

An instance of a BaseCoordinateFrame subclass instance for which to find the WCS

projectionstr

Projection code to use in ctype, if applicable

Returns
wcsWCS instance

The corresponding WCS object

Notes

To extend this function to frames not defined in astropy.coordinates, you can write your own function which should take a BaseCoordinateFrame subclass instance and a projection (given as a string) and should return either a WCS instance, or None if the WCS could not be determined. You can register this function temporarily with:

>>> from astropy.wcs.utils import celestial_frame_to_wcs, custom_frame_to_wcs_mappings
>>> with custom_frame_to_wcs_mappings(my_function):
...     celestial_frame_to_wcs(...)

Examples

>>> from astropy.wcs.utils import celestial_frame_to_wcs
>>> from astropy.coordinates import FK5
>>> frame = FK5(equinox='J2010')
>>> wcs = celestial_frame_to_wcs(frame)
>>> wcs.to_header()
WCSAXES =                    2 / Number of coordinate axes
CRPIX1  =                  0.0 / Pixel coordinate of reference point
CRPIX2  =                  0.0 / Pixel coordinate of reference point
CDELT1  =                  1.0 / [deg] Coordinate increment at reference point
CDELT2  =                  1.0 / [deg] Coordinate increment at reference point
CUNIT1  = 'deg'                / Units of coordinate increment and value
CUNIT2  = 'deg'                / Units of coordinate increment and value
CTYPE1  = 'RA---TAN'           / Right ascension, gnomonic projection
CTYPE2  = 'DEC--TAN'           / Declination, gnomonic projection
CRVAL1  =                  0.0 / [deg] Coordinate value at reference point
CRVAL2  =                  0.0 / [deg] Coordinate value at reference point
LONPOLE =                180.0 / [deg] Native longitude of celestial pole
LATPOLE =                  0.0 / [deg] Native latitude of celestial pole
RADESYS = 'FK5'                / Equatorial coordinate system
EQUINOX =               2010.0 / [yr] Equinox of equatorial coordinates