Ophiuchus is a large constellation located around the celestial equator. It is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Serpens is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput (Serpent's Head) to the west and Serpens Cauda (Serpent's Tail) to the east. They were two of the 48 constellations listed by the 2nd century astronomer Ptolemy and they remain two of the 88 modern constellations defined by the International Astronomical Union. A Celestial Atlas (1822) by Alexander Jamieson, inspired by the star atlas of Johann Elert Bode, but restricted itself to stars that could be seen with the naked eye. Comprising a systematic display of the heavens in a series of thirty maps illustrated by scientific description of their contents and accompanied by catalogues of the stars and astronomical exercises, plate 9, 1822.