CCDs are very cheap, but I was wondering if there was an even cheaper alternative to CCDs if the goal is differential photometry on magnitude 5 and under stars. The data only needs enough precision to prove/demonstrate the concept, and to develop a good sense of the workflow in doing photometry from observational data. Assume I have a 6" newtonian. Photomultiplier tubes such as the 1p21 can be found for less than 40$, but require expensive 1000V power supplies. I am more curious about single photodiodes, or even more crude ways of collecting starlight such as photoresistors. Just wondering if anyone has experimented with some off the beaten path electronic detectors.