* bump *
any cost effective solutions for a camera that will shoot 16+ MP RAW images?
If you look at the supported cameras with >= 16mp, it's not a huge a list. You can check http://chdk.wikia.com/wiki/CameraFeatureTable
and sort by resolution, then check your favorite online retailer for prices. If you are in the US, Canon factory refurbished
is sometimes a very good deal, although I don't see anything really great right now.
In general, it's very hard to give camera recommendations. Most of us only have a few cameras, we can't say how well or poorly CHDK works on the others. Of the cameras I have direct experience with, elph130 and sx160 could potentially meet your criteria. CHDK is reasonably complete on both. There's probably a dozen other cameras that would work equally well, but I have no direct experience with them.
These are cheap cameras, so don't expect amazing image quality.
If you use raw, you will likely have to spend quite a bit of effort on your workflow to get good results.
Setting up a year long timelapse with CHDK will be a fairly technical project and require substantial effort on your part.