I agree. In the first post, I pointed out that there are many other equally important considerations, but perhaps I should reword it to emphasise.
The main motivation for this thread was to add another tool to the toolbox. There are websites out there that tell you how to get the right field of view, how to get the resolution you want, what design of scope might be best, what mount you will need etc etc. But there was nowhere you could go to (that I could find) that would tell you how long you would need to sit out under the stars with the equipment you chose. This tool doesn't quite do that, but it does allow you to see how your system compares with others in terms of sensitivity and also to make appropriate choices when changing something. That has to be better than flying blind and could help you improve your system in a cost effective way - for example, you may have a choice between a $4k camera upgrade for 28% better QE - or - a new scope for $3k with an FNumber of 5.6 rather than 7. This sort of tool will quickly tell you which option will give you the best bang for the bucks. It can also be used for planning imaging sessions - for example, if you like an image on IIS and know the exposure times and equipment used, you can work out how sensitive your system is compared to that used for the original image and estimate how long you will need to image to get the same SNR result.
The 50mm may be ~14x faster, the CDK slaughters it though in the real world. not if you are taking an image of the milky way
