Astrophysics is encrusted with odd conventions that serve as a monument to history, tradition, and the history of measurement technologies. The magnitude system, for example, is, as one of my Astronomy professors put it, "so irrational that it serves just to keep the physicists out." Of course there is the matter of a couple thousand years of history plus more modern questions of measurement that keep it in place. A related notion is measurement of distances in parsecs (and kiloparsecs and megaparsecs) rather than the much more rational (and covariant minded) light years or even meters. Add to that a vast amount of idiosyncratic notation and convention as well as plenty of necessary purely descriptive knowledge and the physicist wonders if he is dealing with physics or stamp collection, in Rutherford's metaphor. The answer, of course, is both.
Astronomy has been and remains more of an observational than experimental science.
One of the more peculiar traditions of astronomy is referring to all elements but hydrogen and helium as "metals". I have no idea where that came from. Any ideas?