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 Capricorn so it is simply ignored.
By the way, the dates that are given for your astrological sun-sign are supposed to indicate when the sun will be in that constellation during the year. In fact, when you think that you are a 'Sagittarius' you are in fact a Capricorn because the Sun is in this constellation during those dates. Astrologers don't care, and no one listens to astronomers when they say that astrology is idiocy masquerading as fact!
Copyright 1997 Dr. Sten Odenwald
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