Why isn Ophiuchus a zodiacal constellation?
Good question! If you look at any star chart, you will see that the narrow path that the planets and the Sun move along, called the Ecliptic, passes through the 12 classical zodiacal constellations, plus it comes within 1/2 degree of the northern corner of Orion, 1/4 degree from the north west corner of Cetus, 1 degree from the north east corner of Sextans, and the entire southern quadrant of Ophiuchus from Ra = 16h 20m to 17h 40m. The problem is that the constellation boundaries have been redrawn several times in the last 5 centuries. Astronomers don’t care, and astrologers only use the classical, ancient definitions of where the zodiacal constellations are located. Ophiuchus would be no doubt an unlucky ’13th house’ between Sagittarius and Scorpius so it is simply ignored. The sun is in this house between November 30 and December 17 each year. For more on this, have a look at the Griffith Observatory article by John Mosley.
