What is a nakshatra?
A nakshatra is one of the twenty seven lunar mansions that the Moon travels through as it circles the sky. Vedic astrologers divide the zodiac of 360 degrees into 27 equal parts of 13 degrees and 20 minutes each, and each part carries its own name, ruling planet and presiding deity. The Moon spends roughly a day in each one before moving on, so the nakshatra it occupied at the moment you were born is treated as your birth star, or Janma Nakshatra.
Where the Sun sign tells a broad story, the nakshatra works at a finer grain. Two people born under the same Moon sign can sit in different nakshatras and read very differently in temperament. For this reason a traditional astrologer reaches for the nakshatra before almost anything else when reading character, naming a child or weighing a marriage match.
How is your birth star found?
Your nakshatra is decided by the exact sidereal longitude of the Moon at your birth. We take your date, time and place, compute the Moon's position with the Swiss Ephemeris using the Lahiri ayanamsa, and then read off which of the 27 segments that longitude falls into. The Lahiri ayanamsa is the standard the Indian government adopted, so the answer matches what a panchang or a temple astrologer would give you.
The Moon moves about thirteen degrees a day, which means it can change nakshatra partway through a single date. That is why birth time matters. If you know your time of birth the reading is exact. If you do not, the calculator assumes noon and tells you so, because the star may shift if you were actually born late in the evening or before dawn.
What are the 27 nakshatras and 4 padas?
The twenty seven nakshatras run in a fixed order, beginning with Ashwini and ending with Revati. Each carries a symbol and a story drawn from the Vedas. Ashwini is the horse headed healer, Rohini is the red one beloved of the Moon, Magha sits with the ancestors, and Revati closes the circle as the nourisher. The full sequence is Ashwini, Bharani, Krittika, Rohini, Mrigashira, Ardra, Punarvasu, Pushya, Ashlesha, Magha, Purva Phalguni, Uttara Phalguni, Hasta, Chitra, Swati, Vishakha, Anuradha, Jyeshtha, Mula, Purva Ashadha, Uttara Ashadha, Shravana, Dhanishta, Shatabhisha, Purva Bhadrapada, Uttara Bhadrapada and Revati.
Each nakshatra is further split into four quarters called padas. A pada spans 3 degrees and 20 minutes and ties the nakshatra to one of the twelve rashis through the Navamsa, the ninth divisional chart. The pada is what an astrologer uses to choose the first syllable of a baby's name, so knowing both your nakshatra and your pada is the practical starting point for a name selection.
Why does the nakshatra matter so much?
The birth star runs through the most personal parts of a Vedic reading. The Vimshottari dasha, the planetary period system that maps out the timing of your life, begins from the lord of your Janma Nakshatra. Match making between a bride and groom counts points through the nakshatras in the Ashtakoota system. Even the daily panchang you might follow for an auspicious moment is built around which nakshatra the Moon sits in that day.
Because so much hangs on it, getting the nakshatra right is worth a little care over your birth details. A correct date, an accurate time and the right place together pin the Moon down to the exact star and quarter, and from there the rest of the chart follows.
Is this nakshatra calculator accurate?
The Moon position behind this result comes from the Swiss Ephemeris, the same astronomical engine used by professional astrology software, set to the Lahiri ayanamsa. There is no rounding to a whole sign and no lookup table standing in for the real position. As long as your birth details are correct, the nakshatra and pada you see here are the ones a careful astrologer would arrive at by hand.