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In short
In a chart, a longitude is a position measured round the zodiac in degrees, 0 to 360, from the start of Aries. Every sign, degree, nakshatra and pada this app shows is read off one sidereal longitude per point. The word also names the birth place's east-west coordinate, which the engine needs to compute the Ascendant.
What the term means
The word has two meanings on this site. The first is celestial: a graha's longitude is its position along the ecliptic, measured in degrees from 0 to 360. Measured from the equinox it is a tropical longitude; with the ayanamsa subtracted it is a sidereal one, and every sign, degree in sign, nakshatra and pada in a chart is read off that single number. The second is geographic: the birth place's east-west coordinate, which fixes the local sky.
Where the term comes from
The BPHS translation uses the celestial sense throughout. Its note to Ch. 3 says the grahas form aspects "through longitudinal distances". Ch. 32 Sl. 1-2 consider two grahas similar "in terms of longitude", and Sl. 3-8 handle Rahu by deducting his longitude in the sign from 30. After a lost birth time is recovered, Ch. 78 Sl. 8-9 say the longitudes of the grahas and bhavas are to be worked out from it. The texts take these positions as given; they do not say how to compute them.
How this app uses it
- Celestial longitudes come from astronomical formulas, measured from the equinox of the birth date, and are then made sidereal. For 19 January 1985, 11:14 IST, New Delhi, the Moon's tropical longitude is 276.30 degrees; less the ayanamsa of 23.64 it is 252.6569, which the engine reads as Sagittarius 12.66, in Mula.
- The geographic longitude of the birth place enters only the Ascendant. Local sidereal time is Greenwich sidereal time plus the place's longitude, so a one-degree error in the place moves the rising point as much as about four minutes of clock time.
- That is why places are resolved, never guessed: from a bundled list, then a geocoding service. Without real coordinates the engine computes no Ascendant at all. The ephemeris page says how accurate the celestial longitudes are.
Pages that use this term
- Why apps disagree on your nakshatra - how one longitude can be labelled two ways.
- When astrology and numerology disagree - the longitudes behind one side of the comparison.
- Kaal Sarp Dosha explained - a rule decided by comparing longitudes with the nodal axis.
- Moon Mahadasha - dasha dates set by the Moon's longitude.
- Birth chart calculator - every point's longitude, sign and degree.
- Methodology - one set of longitudes worked through and checked.
Related terms
- Sidereal zodiac - the frame a Vedic longitude is measured in.
- Tropical zodiac - the frame the formulas start in.
- Ascendant - the point that needs the place's longitude.
- Julian Day - the time input every longitude is computed for.
Birth Chart (Kundli)
All nine grahas by sign, degree and nakshatra, with houses when the birth time is known and the place resolves to coordinates.
This one has its own page
This one runs on its own page, built for it, where the full result is laid out properly. No account is needed there either.