Nakshatra calculator: find your Moon nakshatra

The nakshatras are the 27 lunar mansions of Vedic astrology, also called Jyotish: the sidereal zodiac cut into 27 equal parts of 13 degrees 20 minutes, roughly the distance the Moon covers in a day. Each has a name, a symbol, a presiding deity and a ruling planet. The Moon's nakshatra at birth is often called the birth star, or janma nakshatra.

In Jyotish the Moon is the center of the chart, so the birth nakshatra matters about as much as the Sun sign does in Western astrology. It is read as a color of temperament, and it sets where the Vimshottari dasha, a system of planetary periods, begins. Both are traditions for reflection, not predictions.

Each nakshatra is divided into four padas of 3 degrees 20 minutes. Nine padas make one sign, so the 108 padas of the zodiac match the 108 divisions of the navamsa chart. The pada gives a finer reading and is often used when choosing a name sound for a child.

The calculator shows the Moon's pada from 1 to 4. Because a pada is only 3 degrees 20 minutes wide, the Moon crosses one in about six hours, which is why the birth time matters for it.

The nakshatras are ruled in turn by nine planets: Ketu, Venus, the Sun, the Moon, Mars, Rahu, Jupiter, Saturn and Mercury, repeating three times round the zodiac. Rahu and Ketu are the Moon's nodes. Ashwini belongs to Ketu, Bharani to Venus, Krittika to the Sun and so on, and Revati to Mercury.

The lord of your Moon nakshatra is read as a planet that colors the whole chart, and it opens the Vimshottari dasha: the first period of your life is named after it. The calculator shows the lord next to the nakshatra.

The tropical zodiac of Western astrology is anchored to the seasons, the sidereal zodiac to the fixed stars. Over the centuries the two have drifted apart by about 24 degrees, a gap called the ayanamsa. The calculator uses the Lahiri ayanamsa, the standard in India, so your Moon sits about 24 degrees earlier than in a tropical chart and often in the previous sign.

That is why Vedic and Western astrologers can name different Moon signs for the same birth, with no error on either side. Each works inside its own frame. The sidereal chart calculator shows the whole chart in this zodiac.

The Moon moves between about 12 and 15 degrees a day, close to the width of one nakshatra, so it spends roughly a day in each. If you were born near the start or end of that day, the date alone cannot tell which nakshatra is yours. Without a time the calculator takes midday at your birthplace and says in the card when the Moon changed nakshatra that day.

Add the birth time to settle it. The time also gives the pada and the nakshatra of the ascendant, the lagna, which needs the exact hour because the ascendant changes sign about every two hours.

Every point of a sidereal chart has a nakshatra, not only the Moon. Vedic astrologers read the nakshatra of the ascendant as a second layer on the rising sign, and the nakshatras of the Sun and the other planets as the way each one expresses itself. The calculator gives the Moon and the ascendant, the two that are used most.

The nakshatra of the ascendant needs your birth time; the tool says so instead of guessing. For the signs and houses in the same zodiac, use the sidereal chart calculator.

The calculator computes the Moon's apparent longitude from Meeus's lunar series, subtracts the Lahiri ayanamsa, including nutation, and divides the sidereal longitude by 13 degrees 20 minutes. The whole part gives the nakshatra, from Ashwini at 0 degrees Aries to Revati at the end of Pisces, and the remainder in steps of 3 degrees 20 minutes gives the pada.

We check the sidereal Moon and Ascendant against the Swiss Ephemeris with the Lahiri setting, for charts in both hemispheres, and they agree to within a few arcseconds. Everything is computed in your browser, and the tool is free.