import math


def calculate_coords(star):
	"""
	Calculates Right Ascesion and Declination
	from the X,Y,Z position of a star
	"""
	
	ra = math.atan2(star.y, star.x)
	dec = math.atan2( star.z, math.sqrt(star.x**2 + star.y**2) )
	return (ra,dec)