The more or less horizontal diagonal passing just above the belt of Orion is the Celestial Equator. The horizontal shaded bands at the top represent the southern portion of the zodiac, which is centered on the Ecliptic. The Ecliptic itself is shown by alternating light and dark bands, each of which represents one degree of longitude. The more or less vertical diagonal to the left of Orion is the 6-hour circle, or Solstitial Colure. Its intersection with the Ecliptic is the Summer Solstice. The Ecliptic has the same position now that it had in 1603, but the grid of right ascension and declination has shifted since then; so the Solstitial Colure, which was well to the left of Betelgeuse (Orion's left shoulder, as drawn by Bayer) in 1603, is now much closer to Betelgeuse, as shown in the modern map, below. (Image from the USNO copy of the 1661 edition of Bayer's Uranometria) |
