To know or learn astrology compatibility, we must start by learning how the planets and signs themselves are compatible with each other.
In Indian Vedic astrology the nature of compatibility has been explained in details.
The planets exert different kinds of authority over the Signs they are linked with. Aries is called the Exaltation House of the Sun, although that house belongs to Mars. It means the Sun is very strong in that house. Though there are exaltation houses for other six planets, yet there is a particular degree in them which is termed the Highest Exaltation point.
For an example, the Sun has its highest exaltation at ten degree, it means when the Sun is in Aries and at 10th degree it is said that the native will see the highest effect of the Sun but if it is in 20th degree of Aries it is said he is in his exaltation sun but not in the highest exaltation as he has fallen from the point.
In the same way there is a Sign where a planet is debilitated: the house 7th from the exaltation sign is called debilitation sign of a planet, so the debilitated house of Sun is Libra which is 7th from the Aries. The Sun is in his lowest debilitation if he is in the 10th degree of Libra. Similarly the exalted houses of Moon, Jupiter, Saturn, Mars and Venus are Taurus, Cancer, Libra, Capricorn and Pisces respectively. The debilitated house of these planets is Scorpio, Capricorn, Aries, Cancer and Virgo.
The degree of highest exaltation also varies from planet to planet.
In addition to exaltation and debilitation signs, there is another house is called Mulatrikona house. The Sun’s own house is Leo. This is his Mulatrikona also. The initial 20 degrees portion of Leo is called his Mulatrikona, and the last 10 degrees portion of Leo is his own house or Swakshetra. In Taurus the first 3 degrees constitute the Moon’s exaltation portion and the rest 27 degrees is her Mulatrikona. Similarly for each planet there are defined degrees for Mulatrikona, exaltation or own house.
In Vedic astrology compatibility, Mulatrikona has an important role to play.
Sex of Planets-
The Sun, Mars and Jupiter are males, the Moon, Venus, and Rahu are females, and Mercury, Saturn and Ketu are eunuchs.
The nature of the Planets-
Mercury, Jupiter, and Venus are naturally benevolent, the waxing Moon is benefic. The waxing Moon and Mercury with a malefic are malefics. The Sun, Mars, Saturn, Rahu and Ketu are naturally malevolent. This astrology compatibility is equally good for the people who are governed by these planets.
The Sun, Moon and Jupiter- Pure or Good
Mercury and Venus- Active, Passionate
Mars, Saturn, Rahu and Ketu- Dark, Ignorant
The gems of the planets ( or gems astrology compatibility)-
The Sun- Ruby, Copper
The Moon- Pearl, Lead
Mars- Coral, Bronze
Mercury- Emerald, Brass
Jupiter- Topaz, Gold
Venus- Diamond, Silver
Saturn- Neelam, Iron
Ketu- Lapis Lazuli
There are five elements, and from the properties of these elements we may find out the astrology compatibility of these planets or of the persons who are influenced by these planets.
Fire- Sun and Mars
Water- Moon and Venus
The Sun is the King and Moon is the Queen: Mars the commander, Mercury the crown prince, Jupiter and Venus are ministers, and Saturn the servant.
Mercury governs smell (nose), the Moon and Venus the taste(tongue), the Sun and mars form(eye), Jupiter sound(ear), and Saturn, Rahu and Ketu touch( skin)
The planets have four kinds of aspects. The manner of looking at the 3rd and 10th house from the one occupied by a planet is termed as quarter aspect, looking at the 5th and the 9th is half aspect at the 4th and 8th houses is 3/4th aspect and at the 7th house is full aspect.
There is a specialty in the case of Jupiter, Mars, and Saturn. In the case of Saturn even the quarter aspect is considered to be full. So, he aspects fully the 5th, 7th and 9th houses from the house occupied by him. In the case of a Mars even three-fourth aspect is full. So he aspects fully the 4th, 7th, and 8th houses from the house occupied by him. The Mars and Saturn are among malefics, hence their aspects can not but be malevolent in nature.
Friends and Foes (astrology compatibility of the planets and thus of us)
Friends- Moon, Mars and Jupiter
Enemies- Venus and Saturn
Friends- Sun and Mercury
Neutrals- The Rest
Friends- Sun, Moon and Jupiter
Neutrals- Venus and Saturn
Friends- Sun and Venus
Neutrals- Mars, Jupiter and Saturn
Friends- Sun, Moon and Mars
Enemies- Mercury and Venus
Color- Golden yellow
Friends- Mercury and Saturn
Enemies- Sun and Moon
Neutrals- Mars and Jupiter
Friends- Mercury and Venus
Enemies- Sun, Moon and Mars
Rahu and Ketu-
Friends- Mercury, Saturn and Venus
Enemies- Sun, Moon and Jupiter
Color- Black and Red respectively