While many stars are visible in the night sky, only the brightest are likely to receive enough attention to be named. Names could be given by sailors or anyone else who watches the heavens. These stars are given significance, often heralding an important event, mostly because they were in the sky when something happened. Stars and constellations are not visible all year, for as the planet orbits, the stars overhead change. The same stars will appear each spring, for example. This is also apparent with constellations.
Constellations are an area of world building that can be avoided until we need it. A constellation is a group of stars that suggest an outline of a person or object. They are often attributed mythological significance. In a fantasy setting, people may still believe in such things. In a SF setting, the beliefs may no longer be held true but the constellations may still be recognized. The visible constellations change with the season due to a planet’s orbit around its sun.
Creating constellations that matter to our characters can be done quickly. If we’ve invented gods or other world figures, like those discussed in Creating Life (The Art of World Building, #1), we can use them here. Deities, or objects they possess, such as Thor’s hammer, might be associated with a constellation. Mundane items might also be constellations, like our Big Dipper. People see familiarity and therefore comfort in the stars, and we have great freedom to do as we like.
We should decide which constellations are near each other. This can be done without explanation, as apparent groups of stars have no actual relationship. More important is whether each constellation is near the equator or not. If so, then people in either hemisphere can see it, though it will appear upside down to half the world. Any constellation closer to a pole is only visible to people in that hemisphere. For example, on Earth, most people in the northern hemisphere can’t see the “southern cross” due to its location in the southern sky. This would be a poor location for a constellation we want everyone to see.
If we want each of our gods to have a constellation, we might choose to place all the constellations at the equator so that the whole world can see them. Those living near the poles won’t see all of each constellation, but they’re a minority and we can resolve that concern for most inhabitants, if it matters to us to do so. We might choose to have a god’s constellation only visible in the far north, however, if we want a stronghold of worshippers there and not in the south. What if all evil gods were north and all the good ones south?
If we have a winter god and their constellation is just north of the equator in winter, that makes sense for those inhabitants in the northern hemisphere, but those in the south will see that “winter” god’s constellation in their summer. There is no solution for this unless we decide the god has no constellation or two, one near each pole, where each constellation would never be visible to those in the other hemisphere. The same formation of stars is unlikely, so one symbol might a trident while the other is a fish.
There are also dark constellations (such as the “Emu in the Sky”), which are mostly in the southern hemisphere on Earth and may be unfamiliar to some readers. Clouds of interstellar gas cause these apparent shapes, reminiscent of seeing familiar shapes in rain clouds. They appear dark because they’re so dense as to block light from reaching us. This could be an interesting alternative for the constellations of evil gods. Good gods are light constellations. Evil gods are dark ones.