Exposure relationships

I'm new to CCD work, and am trying to figure out some good guesses for where to start exposures. I know I can look at what others have done, but I need to know some "exposure relationships." To that end, I would like to know:

If I make a perfect exposure of X time, with 1x1 binning, and then increase the binning to 2x2, would my perfect exposure become X/4, and at 3X3 would it be X/9?

I've got another related question about filters, but I believe it is more complicated. So, I'll start another thread for them.

Alex

If you go to 2x2 binning, your exposure time to get the same signal strength on diffuse objects would indeed go to (1/4)X. With 2x2 binning, each pixel is effectively four times the area of a 1x1 binned pixel, so four times as many photons will be hitting it. The trade off, of course, is resolution. You are giving up resolution.

Point sources, by the way, do not behave in quite the same manner. Let's take an example where you are significantly undersampling your image (not unusual for many imagers). I have 9 micron pixels on my camera and a 715mm focal length--significantly undersampled. That means that dim stars often cover only one pixel when I bin 1x1. If I bin to 2x2 or higher, the same number of photons from that point source are going to impact my larger pixel, so I won't get a "deeper" exposure. I will only see exposure time benefits from binning with diffuse objects.