Istar was identified with Nin-si-anna in the first month of the year (Nisan = March-April), with the star of the bow in Ab (August-September), etc. In Sebat (January-February) she was the star of the water-channel, Ikû, which was Merodach's star in Sivan (May-June), and in Marcheswan her star was Rabbu, which also belonged to Merodach in the same month. It will thus be seen, that Babylonian astronomy is far from being as clear as would be desired, but doubtless many difficulties will disappear when further inscriptions are available.
The same fragment gives the celestial names of Merodach for every month of the year, from which it would appear, that the astrologers called him Umun-sig-êa in Nisan (March-April), Dapinu in Tammuz (June-July), Nibiru in Tisri (September-October), Sarru (the star Regulus), in Tebet (December-January), etc. The first three are names by which the planet Jupiter was known.
As for the planets and stars, so also for the constellations, which are identified with many gods and divine beings, and probably contain references, in their names and descriptions, to many legends. In the sixth tablet of the Creation-series, it is related of Merodach that, after creating the heavens and the stations for Anu, Bêl, and Ae,
"He built firmly the stations of the great gods-- Stars their likeness--he set up the /Lumali/, He designated the year, he outlined the (heavenly) forms. He set for the twelve months three stars each, From the day when the year begins, . . . for signs."
As pointed out by Mr. Robert Brown, jr., who has made a study of these things, the "three stars" for each month occur on one of the remains of planispheres in the British Museum, and are completed by a tablet which gives them in list-form, in one case with explanations. Until these are properly identified, however, it will be impossible to estimate their real value. The signs of the Zodiac, which are given by another tablet, are of greater interest, as they are the originals of those which are in use at the present time:--
Nisan (Mar.-Apr.) The Labourer The Ram Iyyar (Apr.-May) /Mulmula/ and the Bull of heaven The Bull Sivan (May-June) /Sib-zi-anna/ and the great Twins The Twins Tammuz (June-July) /Allul/ or /Nagar/ The Crab Ab (July.-Aug.) The Lion (or dog) The Lion Elul (Aug.-Sep.) The Ear of corn(?) The ear of Corn (Virgo) Tisri (Sep.-Oct.) The Scales The Scales Marcheswan (Oct.-Nov.) The Scorpion The Scorpion Chisleu (Nov.-Dec.) /Pa-bil-sag/ The Archer Tebet (Dec.-Jan.) /Sahar-mas/, the Fish-kid The Goat Sebat (Jan.-Feb.) /Gula/ The Water-bearer Adar (Feb.-Mar.) The Water Channel and the Tails The Fishes