Some systems orbit in hours, actually touching each other. Others take years. Star light is extremely feeble and a very sensitive detector is needed. This is an area where a person can do real scientific research with a small telescope even with light pollution of a large city. I designed and build several photometers.
Photoelectric photometers are very sensitive light meters.
My photometers use the photomultiplier approach. I built a photon counting system that could count individual photons coming from stars. I soon had other astronomers contacting me for information on my photometer. I then started to manufacture and sell photometers. The data collected from a photometer must go through many long and tedious mathematical calculations.