Does the addition of the 13th zodiac really changed your zodiac sign?

Answer 1

You're probably thinking of the supposed addition of Ophiuchus, the Snake-Handler, as a "new" sign of the Zodiac. Ophiuchus is not part of the traditional Zodiac, which has twelve signs (corresponding to the twelve New Moons (or Full Moons) in a year. These were marked out and named after the twelve constellations along the line of the apparent path the Sun, Moon and planets (the ecliptic). In one sector of the sky, there are Ophiuchus and Scorpio. Ophiuchus is a fairly faint constellation, while Scorpio is very prominent constellation (in fact, one of the only ones that is even recognizable as what it is said to be). A lot of Scorpio's stars lie well to the south of the ecliptic, but that didn't matter to the astrologers -- they called that sector of the sky after the dominant constellation. And the Moon goes quite a long way north and south of the ecliptic anyway, so the Zodiac is more of a band than a line.

Astronomers are a little more fussy and they have established very fixed, rectilinear boundaries between the constellations, and, according to their reckoning, a segment of the ecliptic line passes through the area they label Ophiuchus. (And very little of the ecliptic line passes through Scorpio.)

However, the band of the ecliptic is a different matter, and anyway the astronomers' boundaries are completely irrelevant to astrologers; on top of which, most western astrologers don't even use a form of the Zodiac that lines up with the constellations.