Hello Roy,
following on from Gary’s reply, welcome to the Variable Star Section!
I’m not sure if you already have your kit or you are looking to buy. If you have some already I suggest you start with that.
I used a 100 mm refractor with a CCD camera for several years for photometry of variable stars. I typically took 60 sec exposures, which enabled photometry down to 15th mag, although I could detect stars much fainter than this. I was lucky enough to have a decent mount so unguided exposures were absolutely fine. It also had GOTO so I was able to find targets easily, but not essential.
There is some info about VS CCD targets here.
Most people are using CCD rather than CMOS. Latter can be used, but you have to be careful about calibration as the response of the chip is less linear.
Hope this helps. Happy to answer further q’s.
Jeremy Shears
VSS Director