Our Universe is very vast and earth is the active member of it. The head of the universe is sun. All the planets and satellites revolve round the sun. Like sun there are numerous stars which revolve in the universe. According to ancient astrologers there are 27 stars, 12 zodiac, and 9 planets presents in the universe.
In Vedic Astrology to know the horoscope knowledge of stars, planets and zodiac is necessary. On the basis of these stars and position of planets in the zodiac astrologers shows horoscope of any person. It is also necessary for them to know time at the birth, date and day, as well as place where he is born. Astrologers make the birth chart of any native on knowing time of birth and position of planets in the universe.
In Indian Astrology the whole universe is divided into a circle of 3600 and if it is divided into 12 parts then each part will be of 300.In this way each part of this 300 is known as galaxy. All these 12 zodiacs are originated through this galaxy. When the stars of the galaxy are joined by imaginary line then they take the shape, like lion, scorpion, sheep, Pisces and so on. In this way all these 12 zodiacs which are originated from galaxy are to be given a symbolic name. From Aeries to Pisces each sign has its symbolic name.
Similarly in the universe this circle of 3600 is divided into 12 parts then each part is of 30 degree is said to be house. Therefore in Indian astrology these 12 houses are also important for these 12 signs. These 12 houses remain always same they have no changes. Only the position of zodiac changes in these houses.
In this way in 24 hours all these 12 zodiacs revolves in galaxy from east to west axis. At the time of the birth the zodiac which rises on the east axis is called first house or Lagna. Each Lagna is only for two hours. In the horoscope of each native zodiac change in the first house or Lagna. In this way in 24 hours all these 12 zodiacs becomes ascendant for only 2 hours.
All these 12 zodiacs are placed in these twelve houses after knowing the position of zodiac in Lagna. In this way after establishing these 12 zodiacs in these 12 houses and knowing about the position of sun, moon and stars in each sign astrologers makes the horoscope of native.
Thus we may say that a horoscope is based on the universe, galaxy and numerous stars and planets found in it.