Please wait In sidereal astrology, there is a branch called "13 sign astrology". This is the only fork of science that considers Ophiuchus as a ecliptical constellation. My astrological service is built on this system, whose zodiacal signs completely coincide with astronomical constellations. But why does 12 sign tropical astrology use Ophiuchus?
People often ask me why natal chart calculation on my site shows incorrect data. That is, the planets, in their opinion, are not in the signs where they should be, and in general everything is different. Since the topic is raised often, and many people simply have not heard about sidereal astrology, which I use, I decided to write a special post and explain why some of my calculations do not agree with generally accepted astrology. Here you can express your opinion and ask questions. 
Since the trajectory of the Sun, when viewed from Earth, has a circular shape, we represent the zodiac as a circle. The circle is divided into sectors (zodiac signs), some of which are located opposite each other. Aries opposes Libra, Capricorn opposes Cancer, and sidereal Taurus is opposed by two constellations at once - Scorpio and Ophiuchus.
Since each zodiac sign has a ruler planet, the opposition of the signs generates a confrontation of the planets. For example, Mars (ruler of Aries) is the exact opposite of Chiron (ruler of Libra), and the Moon (ruler of Cancer) is the opposite of Saturn (ruler of Capricorn).
To clearly see the kinship and enmity of the signs, I made an infographic that reflects the actual planetary properties adapted to the sidereal zodiac. You can trace in which constellation the planet shows its strength and weakness, based on the traditional astrological concepts of domicile, exaltation, detriment and fall.
Everyone knows about classical astrology of 12 zodiac signs because media made it very popular. Someone have heard of vedic astrology, which is based on Indian philosophy; It's actively used by people who are fond of yoga. But few people know about the sidereal astrological system, which is based on real astronomical data. Studying and practicing astrology, I became an adherent of the sidereal approach - its results impressed me very much. To show you visual differences between the tropical, vedic and sidereal systems, I made an infographic. 
Article "Born under the sign of Ophiuchus and ignored by horoscopes: The dilemma of our time" by John Mosley of the Griffith Observatory, which was published in July 1988. In this article, he describes how the signs of the Zodiac differ from the constellations and tells where Ophiuchus came from. 
