The study of ancient sacred sources permits us to say that the ancient Egyptians had a complete set of constellations covering the whole sky that could be seen from Egyptian latitudes. There were two dominant groups, one (probably) in the southern sky and another for northern declinations. The northern sky, as beautifully represented in some New Kingdom tomb ceilings, was full of constellations. These took the form of a lion, a crocodile, a bull's foreleg (sometimes a complete Bull), or a female hippopotamus. The southern group was essentially formed by a belt of 'constellations' known as the decans, individual stars or asterisms whose heliacal rising was presumably used for time-keeping, at least from the end of the Old Kingdom (c. 2200 B.C.), if not earlier, since some decanal stars or constellations, such as sJI} (Sah) or spdt (Sopdet), are already mentioned in the Pyramid Texts. We know this group from the diagonal star-clocks decorating coffin lids (17 have so far come to light) of the First Intermediate Period and the Middle Kingdom, and also from later tombs and temple ceilings, including the famous Zodiac of Denderah (c. 50 B.C.). The system needed to be updated during the Middle Kingdom (c. 1850 B.C.) when the decanal star-clocks were presumably developed, although information about them has been obtained only from a later source known as the Cosmology ofNut, with two relevant extant copies in the cenotaph of Sethy I at Abydos and in the tomb of Ramesses IV (Kings'Valley 2, hereafter KV2).However, in the New Kingdom (c. 1500 B.C.), the decans were no longer useful for time-keeping, due to the wandering character of the civil year, and a new system was developed, using only the meridian (or near-meridian) transit of certain stars, belonging in some cases to huge constellations, such as the Female Hippopotamus (rrt) or the Giant (nb.t), and in others to asterisms. These star charts have been found in the tombs of the last Ramesside pharaohs (c. 1100 B.C.; hence the name "Ramesside clocks or star-charts") in the Valley of the Kings (notably Ramesses VI, VII and IX; KV9, I and 6, respectively), where they were painted for the benefit of the deceased king.The number and variety of documents of astronomical character substantially increases during the New Kingdom and after. As we have mentioned, astronomical ceilings began to depict a complicated pattern, or 'celestial diagram' as it is frequently called, in which lists of stars were combined with actual representations of both southern constellations, such as Sah, Sopdet, sit/srt (Sit or Seret, the Sheep) or wiJ (Wia, the Boat), and northern ones such as mshtyw (Meskhetyu, the Foreleg), msi (the Lion) or rnw(Anu, a falcon-head god). The best preserved, which could be considered masterpieces of Egyptian art, are those found at Thebes in the tomb of Senenmut
