The Rashis (zodiac signs) form the cosmic background through which the Grahas move. At the time of birth, each Graha will be found in one of the 12 Rashis. The Rashi will have a great impact on the condition of the Graha (favorable or unfavorable), as well as its unique qualities. Unlike the tropical zodiac that is used in Western astrology, the Rashis are based on the position of the actual stars. If one compares the nine Grahas to lights that radiate according to our level of awareness in the areas of life explained above, then the Rashis would be like the lamps the lights shine in. The color, shape and qualities of the lamp will have a significant impact on the light inside it, and could help the light get more focused and useful, or it could obstruct the light and discolor it.
The Indian Astrology is Different from Western Astrology which can be clear from the concept of ayanamsha
There are 12 Rashis: