I recently spent three hours trying to track down an algorithm to convert celestial (or equatorial) coordinates to ecliptic. I found several Matlab scripts that

I recently spent three hours trying to track down an algorithm to convert celestial (or equatorial) coordinates to ecliptic. I found several Matlab scripts that purported to work and I tried them in Octave. They never gave answers even close to the NASA Calc [1], so then I searched for something in Python and found pyehpem [2], pulled it down with easy_install, and had the correct answer in two lines of code. [1] http://lambda.gsfc.nasa.gov/toolbox/tb_coordconv.cfm http://lambda.gsfc.nasa.gov/toolbox/tb_coordconv.cfm [2] http://rhodesmill.org/pyephem/index.html http://rhodesmill.org/pyephem/index.html