Nakshatras the Original Skymap
The Nakshatras are Lunar Mansions, (similar to, but not identical with the Lunar Mansions of Chinese Astrology) The 27 Nakshatras of Vedic Astrology are the “behind the Zodiac” segments of the sky. Each Nakshatra is approximately the size of the distance the Moon travels in 24 hours. (While the size of the Nakshatras are constant and fixed, the actual speed of the Moon depends on the distance of the Moon from Earth in any given moment, so the Moon doesn’t actually transit each Nakshatra in exactly 24 hours in an even manner)
The genius of Vedic Astrology is that the Zodiac system (which most likely emerged somewhere in the Fertile Crescent before the heyday of the Babylonian Empire) was superimposed on the much older Nakshatra system. In the Vedic Astrological worldview we have the precision of the pattern of 1 in 27 as opposed to the pattern of 1 in 12. Each Zodiac Sign contains 2 and half Nakshatras, so within each Sign we have 3 possible distinct patterns.
For instance a Scorpio person (meaning a person whose Ascendant is Scorpio) can be Scorpio/Visakha Scorpio/Anuradha and Scorpio/Jyeshta personality.
By the same token, any given planet within the same sign will exhibit distinct characteristics depending on the Nakshatra they are placed in within the Zodiac Sign.
For example Mars in Taurus can be either Mars in Taurus/Krittika, in Taurus/Rohini or Taurus/Mrigasira. These 3 precise placements give added understanding of the energies of Mars in the Birth Chart.
While all 9 planets are analyzed according to their Nakshatra placement, in Vedic Astrology the exact Nakshatra placement of the Moon and the Ascendant (Lagna) point are of the utmost importance. This is one of the reasons why it is impossible to do a Birth Chart without the exact time of birth. The Earth rotates fully in 24 hours (plus 4 minutes) so seen from any location the 30 degrees Zodiac Signs are rising in an average of 2 hours each. Without time of birth it is impossible to determine the Ascendant Sign, much less the Ascendant Nakshatra.
The mindset of a person is by and large seen from the Moon’s exact placement (House placement, Sign placement, Nakshatra placement) and of the conjunctions and aspects involving the Moon. All auspicious and inauspicious days are calculated for everyone based on the exact Moon placement in their Birth Chart. One of the most radically practical and useful gift of Vedic Astrology is the method of finding the best days and best timings for each type of activities. When we start harmonizing with the transits of the Moon in both tangible and subtle ways our whole life becomes better aligned, less stressful, more successful and above all, a lot more fun.
The 27 Nakshatras are ruled by the 9 planets in groups of 3. Each planet (Ketu, Venus, Sun, Moon, Mars, Rahu, Jupiter, Saturn Mercury in this order.)