The 4″ Unistellar you are currently using is quite capable of making useful observations. I am currently using a 4″ Skywatcher Newt to look at variable stars and started submitting results – after a 30 year gap. Working out the magnitudes of the stars is something fun to do on the numerous cloudy nights.
The instrumentation bar to participation in useful observing is very low. A pair of binoculars and a notebook can be a good starting point.