Unlike western astrology, jyotish is based on sidereal time (star time) rather than tropical time (sun time). In other words, the date and time at which each sign of the zodiac begins shifts 20 minutes and 24 seconds every year. A sidereal birth chart thus bears no resemblance to a tropical birth chart for the same point in time, and usually shows a different sun sign.
Jyotish dates back at least as far as the 3rd millennium BC, and is still commonly used to aid in important decisions in modern India. In Hindu culture, newborns are traditionally named based based on their jyotish charts.
Vedic astrology is based on what Western astrologers call the whole house system and recognizes nine grahas (heavenly bodies or "planets"): {| border=1 | Abbreviation | Sanskrit Name | English Name | Represents |- | Sy | Surya | Sun | Soul |- | Ch | Chandra | Moon | Mind |- | Ma | Mangala or Angaraka | Mars | energetic action, confidence and ego |- | Bu | Budha | Mercury | Communication |- | Gu | Guru or Brihaspati | Jupiter | the great teacher |- | Sk | Sukra | Venus | wealth, pleasure and reproduction |- | Sa | Sanaiscarya, Shani, or Śani | Saturn | learning the hard way |- | Ra | Rahu | Ascending/North Lunar Node | often described as a demon who does his best to plunge any area of one's life he controls into chaos |- | Ke | Ketu | Descending/South Lunar Node | supernatural influences |}
They also recognize twelve zodiac signs, or Rashis: {| border=1 | Number | Sanskrit Name | English Name |- | 1 | Mesha | Aries |- | 2 | Vrishabha | Taurus |- | 3 | Mithuna | Gemini |- | 4 | Karka | Cancer |- |5 | Simha | Leo |- | 6 | Kanya | Virgo |- |7 | Tula | Libra |- | 8 | Vrishchika | Scorpio |- | 9 | Dhanu | Sagittarius |- | 10 | Makara | Capricorn |- | 11 | Kumbha | Aquarius |- | 12 | Meena | Pisces |}
One's lagna, or Ascendant, the rashi which is setting on the eastern horizon at the time of one's birth, is the most influential and important one. Of lesser important but still some impact is the Janma Rashi, the rashi in which the moon lay while one was born.
There are two different Jyotish chart notations, which are functionally equivalent but quite different in appearance. The following images show the same birth chart in both notations.
| In the North Indian notation, the house positions are fixed (1st house top middle, with the rest following in counterclockwise order) and the signs of the zodiac are indicated by numbers in the chart (1 for Aries, and so on). | Conversely, in the South Indian notation, the signs of the zodiac have fixed positions (Aries always occupies the 2nd box from the left in the top row, with the rest following in clockwise order), and the first house is marked "As" (for ascendant) with the rest following in clockwise order. |
The charts are broken into twelve sections, houses or Bhavas, each of which is related to a rashi in an equal house system.
