Jeff,
I believe Greg is referring to the following calculator
http://www.ccdware.com/resources/subexposure.cfm
I would suggest using it as a guide, but experiment with what works best. As mentioned in my previous post (in which I apologise for all the typos) you’ll need to review your subs to check your background ADU count for the calculator to work or at least have a greater form of accuracy.
Greg’s recommendation on subs is a good start. It is also what I commonly use 15min lum 1x1 and 10min RGB 2x2. I do also take 20min Ha subs. I’m not worried about having a large calibration library. That is the least of your worries as you can easily refresh the darks in an automated fashion.
MaximDL’s sequencer is indeed a good tool as it rotates through the image sequence ensuring that you build subs across the different filters evenly. This is fine to build experience; however in the quest of improving image quality, the process is not optimal. The reason why I say this is that while the object is rising, you may not want to collect blue filtered or luminance data due to atmospheric extinction scattering light or low resolution. Hence, while the object is rising, you may only want to collect red filtered data that is not compounded by atmospheric extinction. A common method I use in data acquisition is a stepped approach. As the object rises, I collect red filtered data. Once it hits approximately 70 degrees start collecting green, then followed by blue. This minimises the scattering of blue light. As the object approaches meridian or is as high as it will get, collect luminance to improve resolution. So the sequence is RRGGBBLLLLBBGGRR as it crosses the meridian. This is somewhat off topic considering we are not talking exposure times, but it re-emphasises the point that you’ll go to extremes to ensure you collect quality data, even if that includes a few long exposures.
Indeed, Scott. You nailed it... you need cooling for long subs to be effective. Some good info for DSLR users can be review here -
http://www.samirkharusi.net/sub-exposures.html