celestial_frame_to_wcs

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

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:

frame : BaseCoordinateFrame subclass instance

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

projection : str

Projection code to use in ctype, if applicable

Returns:

wcs : WCS 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