Using to_radians

Signed-off-by: Paulo Roberto Urio <jimmyskull@gmail.com>
Converting coordinates and computing star's masses

Except for proper motion values, the star position is now
converted from celestial to cartesian coordinates.  Also, we're
computing the star's masses using the mass-luminosity relation.
Signed-off-by: Paulo Roberto Urio <jimmyskull@gmail.com>