NAME:
ll
PURPOSE:
return Galactic longitude
INPUT:
t - (optional) time at which to get ll
obs=[X,Y,Z] - (optional) position of observer (in kpc) (default=[8.5,0.,0.]) OR Orbit object that corresponds to the orbit of the observer
ro= distance in kpc corresponding to R=1. (default: 8.5)
OUTPUT:
l(t)
HISTORY:
2011-02-23 - Written - Bovy (NYU)
