[amsat-bb] Pass prediction algorithm

I'm trying to write my own pass prediction program for tracking FM satellites. This program will this notify the users of upcoming passes via APRS messaging. I would like to find an algorithm that will predict AOS/LOS time and azimuth and the maximum elevation. I'm also hoping this algorithm will not be too computationally intensive as it may possibly be used for hundreds of different station locations.

Can anyone help?

73, Reid N0RC