rubin_sim.utils.apply_precession(ra, dec, epoch=2000.0, mjd=None)

apply_precession() applies precesion and nutation to coordinates between two epochs. Accepts RA and dec as inputs. Returns corrected RA and dec (in degrees).

Assumes FK5 as the coordinate system units: ra_in (degrees), dec_in (degrees)

The precession-nutation matrix is calculated by the palpy.prenut method which uses the IAU 2006/2000A model

@param [in] ra in degrees

@param [in] dec in degrees

@param [in] epoch is the epoch of the mean equinox (in years; default 2000)

@param [in] mjd is an instantiation of the ModifiedJulianDate class representing the date of the observation

@param [out] a 2-D numpy array in which the first row is the RA corrected for precession and nutation and the second row is the Dec corrected for precession and nutation (both in degrees)