Perseus is bordered by Camelopardalis and Cassiopeia to the north, and Andromeda and Triangulum to the west. Triangulum is a small constellation in the northern sky. Its name is Latin for triangle, derived from its three brightest stars, which form a nearly isosceles long and narrow triangle. They were three of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remain three of the 88 modern constellations defined by the International Astronomical Union. The Atlas Coelestis is a star atlas published posthumously in 1729, based on observations made by the First Astronomer Royal, John Flamsteed. The first comprehensive telescopic star catalogue and companion celestial atlas, contains 26 maps of the major constellations visible from Greenwich, with drawings made by James Thornhill. One of his main motivations to produce the Atlas, was to correct the representation of the figures of the constellations, as made by Bayer's, Uranometria (1603). Bayer represented the figures viewed from behind (not from the front, as was done since the time of Ptolemy), which reversed the placement of stars and created unnecessary confusion.