I see. Much clearer now. There is no-way I could have foreseen those values at those speedcurves. Your sliderule needs some sort of legend there to identify the scale of the curves. [EDIT: WHoops. I didn't look at the top of page 2 good enough, ...how did those scales get in there so quick.
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But here's my main inconvenience (I guess I didn't get across more eloquently before), why manually calculate range based on observed-fov (the 4.9/2.75=1.78; but maybe not neccessary anymore in your next version), or manually calculate the 'true time' (7s/1.78=3.9), if you allready have a (logarithm-based) tool in front of you that should do the job? Those divisions are piece of cake for log-sliderulers. It just needs clever use of scales.