Right ascension is the celestial latitude. Thus, as the Earth rotates, the right ascension of the zenith changes. In one hour of rotation, the right ascension changes by 1 hour as well. Thus, these expensive computations are not done at every display. Thus, there are approximately 60,000 points that are converted upon initialization.
Stellar magnitude is on a logarithmic scale.
The difference between a single magnitude level is 2.512 times the brightness. This number was chosen so that the difference of 5 levels of magnitude is exactly 100 times brightness. StarGaze also converts the magnitude to an integer between 0 and 255, since this is what OpenGL uses to determine the brightness of a pixel. This formula was chosen because it closely approximates the visible magnitude of the stars in the sky. The software computes numerous astronomical calculations.