Comment 1 for bug 965811

Your code is asking "if one object appears at the horizon and another at 0.1 radians above it (about 5.729578°) then what is the REAL angle between them on a star chart?" And since the atmosphere artificially curves the image of objects upwards near the horizon, two objects must in reality be farther apart than 0.1 radians to APPEAR a mere 0.1 radians apart in altitude in the sky.

To turn off the effects of the atmosphere, set "obs.pressure = 0" and the separation2 should be very close to 0.1 — I am not finding that it is EXACTLY equal, but that might be because of the trig functions not wanting to work exactly backwards — or is there another slight effect besides atmospheric distortion that I am forgetting about? :)