galpy.util.coords.pmrapmdec_to_pmllpmbb(pmra, pmdec, ra, dec, degree=False, epoch=2000.0)[source]

Rotate proper motions in (ra,dec) into proper motions in (l,b)

  • pmra (float or numpy.ndarray) – Proper motion in ra (multiplied with cos(dec)) (mas/yr)

  • pmdec (float or numpy.ndarray) – Proper motion in dec (mas/yr)

  • 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)


[pmll x cos(b),pmbb] in (mas/yr,mas/yr). For vector inputs [:,2]

Return type:

tuple or numpy.ndarray


  • 2010-04-07 - Written - Bovy (NYU)

  • 2014-06-14 - Re-written w/ numpy functions for speed and w/ decorators for beauty - Bovy (IAS)