3 thoughts on “What is the difference between Tropical and Sidereal regions in western astrology?

  1. Tropical Zodiac. Most people know what their birth sign is. They may be a “Leo” or a “Taurus” or one of 10 other signs of the Tropical Zodiac. What does it mean? It means that at the time of their birth, from an earth perspective, the sun was in 1 of 12 zones around the earth. Each of the 12 has an angular length of 300. 12 X 300 =3600. The frame of reference for these zones is the sun’s positions relative to the earth’s horizon. As the sun moves through the seasons its altitude changes and so do the compass bearings of its rising and setting positions. None of these signs can be directly related to a group of stars that can be seen in the skies with one’s physical eyes.

    Sidereal Zodiac- it is important to clarify the use of two words. When the word ‘sign’ is used in this article it refers to the Tropical Zodiac and ‘constellation’ refers to the Sidereal Zodiac. Both zodiacs are divided into twelve and they both use the same names, which understandably causes enormous confusion. If your birth ‘sign’ is Pisces it does not necessarily mean that the sun was in front of the ‘constellation’ of Pisces at your birth. Your birth ‘constellation’ is different to your birth ‘sign’. What earth season (i.e. sun declination or latitude) you were born in is different to what stars where behind the sun at the hour of your birth. The Sidereal Zodiac uses the physical stars visible in the night sky as their frame of reference for the sun, moon or planet’s positions in the sky. The sun, moon and planets do not transit in front of all the constellations in the sky, they only traverse in front of 12 or 13. These are the zodiacal constellations. Whether there are 12 or 13 depends on where the boundaries for the various constellations are positioned. Different cultures and systems have positioned them differently i.e. there is no universal consensus to the boundaries or even to the size of the constellations. Generally speaking the sidereal zodiac (as seen by a person standing on the earth) is that belt of stars 70 either side of the sun’s path (ecliptic) through the sky that is divided into 12 equal sized (300) constellations.

  2. Sidereal is accurate since it holds the current place of the constellations (signs), whereas Tropical is based on where the constellations (signs) were over 2,000 years ago.

    edit: If you look up zodiac, you’ll get “contains twelve constellations and hence twelve divisions called signs of the zodiac.”

  3. Actually neither system uses the constellations as anything more than a reference point for where their zodiac starts. A zoidia (or zodiac sign) is *not* the same thing as the constellation it shares a name with.

    Both zodiacs start at 00 degrees of Aries, but:

    Tropical astrology says 00 Aries starts at the Spring Equinox. Sidereal astrology says 00 Aries is when the Sun gets to the constellation of Aries, but this is just a reference point.
    There’s about a 23-24 degree difference between the two systems right now.

    The zodiac is a band of 12 (and only 12!) 30-degree segments of space around the Earth, whereas the constellations are all uneven in length. Astrology uses the zoidia (zodiac signs), not the constellations. (Though there are astrologers that work with individual stars, but that’s another subject entirely. 🙂

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