thanks John. You are right that the binning will give 1.5 hours rather than 2 hours - the table has been changed to reflect that - thanks for the correction
(I hope that it is now right). However, for the 1x1 binning in strategy 1, the total RGB time given is 6 hours (2hrs each), so I think that the total RGB time with 2x2 binning is 1.5 hours (0.5 hrs each rather than 1.5 hours each) and the total time is 7.5 hrs rather than 10.5hrs.
The luminance SNR of the RGB strategy will be determined by the total number of photons detected. Since each RGB will have ~1/3 the photon flux of the full broadband luminance (due to the filters), the total number of photons detected in any given time will be ~1/3 of those detected broadband - ie you need 3x the time to get to the same luminance SNR from the RGB strategy as you would with full luminance broadband. The colour data from the RGB strategy will of course have much better SNR than the colour from strategy 1. The RGB strategy cannot be made directly comparable with the others in this type of comparison, so I specified that the luminance SNR should be equivalent - with the note that the colour data will be better than that from other strategies. I have no idea how much difference the extra colour SNR makes, but many people use straight RGB very effectively. I guess the other thing that might be important is that RGB imaging will give better resolution than lum+RGB if the scope has any CA - may be important for some refractor users.
Once again, thanks very much. ray