If you're interested in this type of computation and have some basic knowledge of Python, there is a package called pyephem that you can install that allows you

If you're interested in this type of computation and have some basic knowledge of Python, there is a package called pyephem that you can install that allows you to perform all sorts of calculations on the planets and other astronomical bodies. It uses the same ephemerides data set that is used by professional astronomers so it is quite accurate.