I'm rural as well, but not many old sat dishes left around here.
Never thought about a wiper motor I likely have a few kicking around, this motor I have is way more than needed

 

Photocells don;t sound like a good idea. Passing clouds, a rainy day will cause undesirable results.

I'd recommend as Astronomical TImer. these times calculate sunrise and sunset, Usually you can program them to active before or after the computed time. It will avoid the daily fiddling. I have one light on one. On about an hour after dusk and off at 11:30.

The alarm switches are probably reed switches. You can probably find a hall effect switch to use and you might start getting fancy. Put your Arduino skills to work and use an H-bridge and maybe add a current sensor to detect stall as a safety https://www.pololu.com/category/118/current-sensors