... looks like "magnitude" numbers farther below zero are brighter? Who came up with that?
> The scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars in the night sky were said to be of first magnitude (m = 1), whereas the faintest were of sixth magnitude (m = 6) [...]
> In 1856, Norman Robert Pogson formalized the system by defining a first magnitude star as a star that is 100 times as bright as a sixth-magnitude star, thereby establishing the logarithmic scale still in use today. This implies that a star of magnitude m is about 2.512 times as bright as a star of magnitude m + 1. This figure, the fifth root of 100, became known as Pogson's Ratio.
Hmmph. I'd prefer a system where higher numbers were brighter, and probably with a different logarithmic base. Oh well.
The Pogson system was constrained by the compatibility with the legacy star classification.
The stars had already been described for millennia as being stars of the 1st magnitude, 2nd magnitude and so on, from the brightest to the less bright.
Pogson has chosen both the logarithmic base and the sign of the magnitude which makes higher number less bright, so that the magnitudes computed by his formula will match approximately the already existing classification of the stars.
It was fortunate that the simple rule that a difference of 5 in magnitudes corresponds to a brightness ratio of 100 gave a formula which produced magnitude values that, when rounded to integers, matched in many cases the traditional magnitudes of the stars.
I have watched the ISS go overhead in the middle of a very sunny cloudless Los Angeles day. It can be very visible, when you know the timing & direction.
The ISS, which has five times more modules, reaches magnitude -4 sometimes. Third brightest thing in sky.