Jyotisha is used for astronomical studies as well as astrology.
As we all know astrology is based on planetary movements through the rasis. There are 12 rasis (Sign), but these days astrologers, especially western astrologers are discussing the possibility of a 13th rasi, which is known as Ophiuchus.
The main text of Vedic astrology is a collection of verbal teachings by Sage parasara, is the man behind Brihat Parasara, which is known as the main text for all the vedic astrology. The other main texts of Vedic astrology are Jaimini Sutra, Bhrigu sutra and Phala dipika. All these texts are describing these rasis are the main unit of astrology.
In chapter 4 of Brihat parasara Hora sastra, 12 Rasis are known as the limbs of Kaal Purush.
“Kaal Purush” is also known as “Virat Purush”, in English it is “Cosmic Man”. Everything is consumed by time, but the Virat Purush is unconsumed by the time. He is beyond the human perception. He is so massive and the entire akasha is his abode.
Entire zodiac is 360 degrees and each rasi is expands up to 30 degree.
Aries/Mesh: It is the first rasi in the natural zodiac when. Aries represents the head of Kaal Purusha. It is a fire rasi and ruled by Mars. The dwelling of this rasi is in forest. The Sun gets exalted in this rasi. It has a Quadruped body. It is a prishtodaya rasi well. This is a male rasi. This rasi rules east.
Vrishabh/Taurus: This is the second rasi of the natural zodiac wheel and it is ruled by Venus. This rasi represent agricultural land with water. This is a quadruped rasi. Vrishabh is an earth rasi as well. This is a prishtodaya rasi as well.
Mithun/Gemini: This is an air rasi and it is ruled by Mercury. It rules bedroom. This is a human rasi and sheershodaya rasi. This is the third rasi on the natural zodiac.
Kark/Cancer: This is the fourth rasi and a water rasi. It is ruled by Moon. This is the only rasi ruled by the Moon. This rasi represents places with water. It is a watery rasi and. This is a prishotdaya rasi.
Simha/Leo: This is the most royal rasi and it is rule by Sun. This is the only rasi ruled by the Sun. This is a quadruped rasi. It rules mountains. This is a sheershodaya rasi. Leo is a fire rasi too.
Kanya/Virgo: This is an earth rasi and it is ruled by Mercury. Virgo is a sheershodaya rasi and human rasi too. This rasi rules places with water and food.
Thula/Libra: It is ruled by Venus and is an air rasi. It represents the house of a vaishya. This is a sheershodaya rasi.
Vrischik/Scorpio: This is a water rasi and is ruled by Mercury. Moon is debilitated in this rasi. It represents a cavity or hole. This is a sheershodaya rasi. This is a centipede rasi as well.
Dhanu/Sagittarius: Dhanu is ruled by Jupiter and is a fire rasi. It represents palace where the King lives. Its first half is a human rasi and second half is quadruped. This is a prishtrodaya rasi as well.
Makar/Capricorn: This is an earth rasi and it is ruled by Saturn. This is a prishtodaya rasi and its first half is quadruped and later half is watery as well. It rules watery forests.
Kumbha/ Aquarius: This rasi represents the gathering place for potters. This rasi is ruled by Saturn and is an air rasi. It is a sheershodaya rasi as well. It is a human rasi.
Meen/Pisces: This is an Ubhayodaya rasi. It is a centipede rasi as well. Ruled by Jupiter, this rasi is a watery rasi.
Movable rasis or Chara Rasis: Mesha (Aries), Kataka (Cancer), Tula (Libra) and Makara (Capricorn)
Fixed rasis or Sthira Rasis: Vrishabha (Taurus), Simha (Leo), Vrischika (Scorpio) and Kumbha (Aquarius)
Dual rasis or Dwi Swabhava rasis: Mithuna (Gemini), Kanya (Virgo), Dhanus (Sagittarius) and Meena (Pisces)
Direction ruled by Rasis
East – Aries/Mesha, Leo/Simha and Sagittarius/Dhanu
South – Taurus/Vrishabha, Virgo/Kanya and Capricorn/Makara
West – Gemini/Mithuna, Libra/Tula and Aquarius/Kumbha
North – Cancer/ Karak , Scorpio/Vrischika and Pisces/ Meena
Masculine or Odd Rasis: Aries, Gemini, Leo, Libra, Sagittarius, Aquarius,
Feminine or Even Rasis: Taurus, Cancer, Virgo, Scorpio, Capricorn, Pisces.
Since the zodiac is known as the body of Kalpurusha, each rasi represents the body parts
Aries: Complexion, head cranium, forehead and brain, hair, pituitary glands
Taurus: face and its organs, facial bones, upper neck and its bones, gullet, larynx, cerebellum, trachea, cervical region and cervical bones, tonsils
Gemini: lower neck, shoulders, arms and ears, hands, shoulders and collar bones, thyroid gland, respiratory and nervous systems
Cancer: rib cage, heart, chest, lungs and breasts.
Leo: upper belly, stomach, liver, gall bladder, pancreas, spleen, colon, diaphragm, spine and spinal cord, pregnancy
Virgo: waist, navel, lower abdomen, kidneys, small intestine, upper part of large intestine, intestinal function, appendix
Libra: pelvic girdle, lumbar region, bladder, lower part of large intestine, inner sexual organs such as ovaries, uterus, cervix, testicles and prostate gland
Scorpio: scrotum and anus, outer sexual organs, excretory organs, pelvic bones
Sagittarius: thighs, left leg, thigh bones, bone marrow, hips, hip joints and the arterial system.
Capricorn: knee and kneecaps, joints and bones
Aquarius: lower portion of legs, pain in legs, problems of low productivity of blood, cancer of leg
Pisces: left eye, lymphatic system and feet
These rasis rule each house. There are tweleve rasis and twelve rasis. Planets move through these rasis. Each horoscope has different features; they are different from each other. It shows different destinies of human despite geographic location. For a clear and accurate analysis, we must learn all the minute detail of all the features of the chart. In that rasis have a big role.