"Our lives are but a moment, compared to the life of a star." -Lago-Charago, a Tarutaru who maps out the starts from the top of the Opistery in Windurst.
The constellation of Odin sits in the Northern sky, with a black point in the middle, which marks his favorite horse, Slepnir. Other avatars include, Ifrit, Leviathan, Ramuh, Titan, Garuda, Shiva and Alexander, which are all represented by constellations. Furthermore, you can see a Chocobo and Moogle, as well as several monsters: Tonberry, Behemoth, Vulture, Bomb, and Cactuar, all represented by constellations.
ベヒーモス座 - Behemoth A large constellation in the far Northern sky. This great curve of stars is meant to represent the gargantuan Behemoth's massive horns. They say it appears as if it is about to be vanquished by Odin.
サボテンダー座 - The Cactuar A cross-shaped constellation in the middle of the stellar map. Of course, this particular grouping of stars is associated with those succulent little Sabotenders that roam the desert. One time, a group of meteors was observed falling from the location of the central star and was dubbed the "Thousand Needles Shooting Star."
死鳥座 - The Vulture A set of stars in the central sky shaped like the "V" of a vulture's flapping wings. One tale speaks of how the Vulture appeared when Ifrit's soul was rising into the sky through use of the sordid magic, which brought his companion to meet him.
チョコボ座 - The Chocobo A large constellation in the Eastern sky. The arrangement of stars makes it easy to spot the Chocobo from any region. However, some say the Chocobo is Shiva's mount, Kanyawa, and some say it is Garuda's child, Upasha. It depends on what town you are viewing it from.
トンベリ座 - The Tonberry A set of stars, visible in the Southern nighttime sky, that resemble a Tonberry. Which star represents which part is something that is debated from region to region, (probably because many don't know what a Tonberry looks like), the large knife, the lantern, and the hood are what most people know about. It is said the Tonberry is aiming for Daemdalus, the main star of Titan.
ボム座 - The Bomb The Bomb is made up of three stars visible in the Southern nighttime sky. According to Sand'Orian scriptures, Ramuh awakened the Bomb by striking a mountain with his lightning bolt, engulfing it in flame and bringing fire to the people. The gods were angered by this and summoned Leviathan from the Western ocean to douse the flames, killing the inhabitants.
モーグリ座 - The Moogle A small constellation in the Southern sky. The one red star that is slightly separated from the rest represents the Moogle's unique head-piece. According to a folk-tale, this Moogle is Kupilfin, and has flown towards Titan out of concern for Daemalus.
Some/all of the information in this article has been culled from various FFXI guides, and translated by Elmer the Pointy.