What sensor to use for sensing azimuth & altitude of satellite dish?
A stationary object may use an accelerometer to reasonably accurately determine which direction is down (or, conversely, up) without needing any sort of reference other than a large nearby planet.  In theory, a sufficiently-precise gyroscope could also determine which directions were north and east without needing any sort of reference other than being affixed to a large nearby planet which is turning on a north-south axis, but I doubt that any commercially-available electronic gyroscopes would achieve that level of precision.

If you have a base whose alignment is fixed, and merely wish to measure position relative to that, potentiometers can be pretty good.  When they are used in a ratiometric fashion, they can be relatively precise and also immune to changes in temperature, humidity, etc.