Orthodox Asterism was the official religion under the Elvish Empire. At the time of that Empire’s fall, human Asterists underwent some internal purging because of their collusion with elvish oppression of humans, but as human high culture is, basically, elvish culture, Asterism remained the religion of the (now human) ruling classes and most urban people. It was once the case that Asterists were primarily descended from house slaves and Earthists from field slaves, though it has been so long since the Fall of the Elven Empire that this is only approximately true any more.
Even in the country and among Earthists, the local Asterist scholar is still highly regarded by most people – for his or her learning, if nothing else - and people who are otherwise basically Earthists in practice will show up for the occasional moon ceremony. The relationship between the scholars and the local Earthist mystics varies from mutual public denunciation to complete collegiality, depending as much on the personalities involved as anything else. Rural scholars are often ascetic and devout (and rather vague about worldly matters), while urban scholars are more likely to join the powerful whom they advise in a degree of worldly indulgence and display.
Asterist ceremonies follow the lunar cycle and the seasonal stars. The numbers three and nine, and their significant multiples, are considered sacred and figure largely in ceremony, symbolism and practice. The cosmology recognizes a divine power which manifests in three aspects (the Origin, the Centre and the Destiny), each with three faces. The Lifegiver, the Lifesustainer and the Lifetaker are the female faces, the Planter, the Grower and the Harvester the male faces, while the Maker is both male and female at once, the Changer either male or female alternately, and the Ender neither male nor female.
Elves are, in a sense, Asterists as well, of course, but the comparison is rather like that between a very conservative "high" Tridentine Catholic (the elves) and a rather liberal, rather "low" Anglican (the average human Asterist).
The elvish practice is that priesthood resides in rulers and the senior members of families (male and female equally), but the priests are assisted by professional religious scholars who study the ways of the divine and instruct the priests in their ceremonial duties. This approach was passed to human Asterism (and has affected Earthism as well, in that the heads of families function as priests there also). Often, married couples are both scholars.
It is, of course, possible to be both a priest (by position) and a scholar (by training) simultaneously.
The scholars belong to a number of Asterist Orders, large and small, founded with different missions at various times. Some are teachers, some researchers, astronomers, mathematicians, musicians, historians, and so forth (in some orders, several of these are combined). Most are politically involved, a natural role given that they advise the rulers on their priestly duties, which are in turn intimately entangled with the running of the nation.
Someone acting as an Asterist priest wears a belt representing constellations, with a sun buckle.