... engineering students like me .. thinking about figuring out at exactly what elevation the satellite is when to change between downlink frequencies ...OK, now - although this IS rocket science, it really isn't. (grin)
Even with a very directional Yagi, you have quite a bit of "leeway" while working the FM satellites. I mean, it is not as if you're rigidly holding the antenna ... making minute movements every fifteen seconds ...
Do not over-think this. Just get outside and DO IT!
(Apologies to Nike.)