galpy.util.coords.cov_pmrapmdec_to_pmllpmbb(cov_pmradec, ra, dec, degree=False, epoch=2000.0)[source]

Propagate the proper motions errors through the rotation from (ra,dec) to (l,b)

  • cov_pmradec (numpy.ndarray) – Uncertainty covariance matrix of the proper motion in ra (multiplied with cos(dec)) and dec [2,2] or [:,2,2]

  • ra (float or numpy.ndarray) – Right ascension

  • dec (float or numpy.ndarray) – Declination

  • degree (bool, optional) – If True, ra and dec are given in degrees (default=False)

  • epoch (float, optional) – Epoch of ra,dec (right now only 2000.0 and 1950.0 are supported when not using astropy’s transformations internally; when internally using astropy’s coordinate transformations, epoch can be None for ICRS, ‘JXXXX’ for FK5, and ‘BXXXX’ for FK4)


covar_pmllbb [2,2] or [:,2,2] [pmll here is pmll x cos(b)]

Return type:



  • 2010-04-12 - Written - Bovy (NYU)

  • 2020-09-21 - Adapted for array input - Mackereth (UofT)