These are chat archives for astropy/astropy
akk on FreenodeHi -- I have a program where I'm plotting Mars' retrograde loop and calculating things like opposition and closest approach
akk on Freenodetrying to calculate opposition by doing mars = get_body('mars', cur_time); sun = get_body('sun', cur_time); elongation = (mars.ra - sun.ra) and use that to determine opposition
akk on Freenodeand PyEphem gets the right answer, but AstroPy sees it happen on the wrong day, and it also shows the planet approaching and receding several times during the month.
akk on FreenodeI'm wondering, does get_body(name, time) calculate from some specific point on earth even though I deliberately don't specify one, so I'm seeing parallax issues?
akk on FreenodeAny advice on calculating opposition/elongation? I seem to be getting the wrong values from get_body('mars', cur_time).ra - get_body('sun', cur_time).ra.
akk on FreenodeI'm getting apparently wrong answers for distance too, so I wonder if get_body is measuring from some moving point on earth.