NAME:
helioX
PURPOSE:
return Heliocentric Galactic rectangular x-coordinate (aka “X”)
INPUT:
t - (optional) time at which to get X
- obs=[X,Y,Z] - (optional) position and velocity of observer
- (in kpc and km/s) (default=[8.5,0.,0.,0.,235.,0.]) OR Orbit object that corresponds to the orbit of the observer
ro= distance in kpc corresponding to R=1. (default: 8.5)
OUTPUT:
helioX(t)
HISTORY:
2011-02-24 - Written - Bovy (NYU)