pm_gal_to_icrs

gala.coordinates.pm_gal_to_icrs(coordinate, pm)[source]

Convert proper motion in Galactic coordinates (l,b) to ICRS coordinates (RA, Dec).

Parameters:

coordinate : SkyCoord, BaseCoordinateFrame

An instance of an Astropy coordinate object. Can be in any frame that is transformable to ICRS coordinates.

pm : Quantity, iterable

Full description of proper motion in Galactic longitude and latitude. Can either be a tuple of two Quantity objects or a single Quantity with shape (2,N). The proper motion in longitude is assumed to be multipled by cosine of Galactic latitude, \(\mu_l\cos b\).
Returns:

pm : Quantity

An astropy Quantity object specifying the proper motion vector array in ICRS coordinates. Will have shape (2,N).

Examples

>>> import astropy.units as u
>>> import astropy.coordinates as coord
>>> c = coord.SkyCoord(ra=196.5*u.degree, dec=-10.33*u.deg, distance=16.2*u.kpc)
>>> pm = [-1.53, 3.5]*u.mas/u.yr
>>> pm_gal_to_icrs(c, pm) 
<Quantity [-1.84741767, 3.34334366] mas / yr>