What a week it’s been, stargazers. First, we were told our Zodiac signs have changed , that there's now a 13th sign, and that apparently everything we believed up to this point was a lie. Then, NASA reminded us that astronomy and astrology are wholly separate disciplines, so we relaxed a bit. Once the dust settled, we were able to step back, learn a bit about Ophiuchus , and maybe even make our peace with it. After all, you only need to observe this 13th sign if you follow sidereal astrology (rather than what we practice here in the western world, tropical astrology). Sidereal and tropical astrology mainly differ in how their respective horoscopes are created — hence the added Ophiuchus sign. More specifically, they use different methods to determine the date ranges for their signs — methods that also dictate how astrologers in each discipline make their predictions.Sidereal astrologers use the positions of fixed star systems and constellations, while tropical astrologers look to the sun’s position in relation to the earth. So, sidereal predictions tend to name when and how specific events will occur — it’s for this reason that many consider them more precise and reliable. Meanwhile, tropical predictions tend to pertain more to the individual and his or her psychological state and rarely take as wide a look at the future.