help with choice of CCD

I am a total newbie when it comes to observing. I really want to start collecting photometric data for scientific analysis but do not know which CCD camera to buy. I have very limited funds and can't afford SBIGs or QHY priece range. I would have to save up to buy a $3-400 CCD.

What is the cheapest CCD I can buy to do useful work. I have an 800mm refractor with a serious goto mount

Also where can I find the specific filters used for photometry

Alex

aka Astrovouk