I'm trying to find the appropriate formula (and abstractions to plug into it as necessary) to work out the absolute magnitude (from which I can dervive an apparent magnitude) of a solar body. I've found a lot of formula which relative absolute and apparent magnitude, but trying to find how to calculate the former is proving really hard - especially since planetary bodies use a slightly different system. Wiki - ironically, considering I google searched for ages - has been most helpful so far (which is not very), especially with the moon example. With just one problem - the Hmoon value. From what I'm understanding, that's the moon's absolute magnitude (so that formula is for the apparent magnitude). But it doesn't appear to say anyway where that's dervived from. It says something about subtracting 31.57 from something to get the planetary as opposed to stellar magnitude... Trouble is, the wiki page on the moon doesn't give you that information, so I can't back-work the numbers to get where Hmoon is coming from. What I am looking for is a first order approximation of absolute magnitude for a stellar body, given I know the luminosity of the star, the size, distance (or the stellar flux, since I've already got that calculated) and the body's albedo. (I am assuming maximum, so the phase angle wouldbe 0º if I understand right.) Can someone point me in the right direction?