Special lagna calculators disagree mainly over sunrise, which the Brihat Parashara Hora Shastra does not define. Taking sunrise at the upper edge of the Sun or at its centre moves Ghati Lagna by about one and a half to two degrees, enough to change its sign near a sign boundary. The other causes are four schools of Varnada Lagna, an old Pranapada error, and Sree Lagna magnifying small Moon differences.
How we tested
We used only answers that anyone can look up. Jagannatha Hora is a widely used desktop program for checking results, and its full special-lagna output has been published for two historical charts drawn up for Philadelphia: 4 July 1776 at 5:51 pm and 7 July 1920 at 3:32 pm, local time. The textbooks add worked arithmetic: R. Santhanam’s translation of the Brihat Parashara Hora Shastra, P.V.R. Narasimha Rao’s textbook, and a published Sree Lagna lesson for 4 April 1970.
We ran every chart through the same engine that powers our calculators, once with the sunrise Jagannatha Hora used (the moment the centre of the Sun’s disc rises) and once with the sunrise our panchang pages and calculators use (the moment its upper edge appears). All positions are sidereal, with the Lahiri ayanamsha.
Jagannatha Hora’s published charts, side by side
4 July 1776, 5:51 pm, Philadelphia
| Lagna | Jagannatha Hora (published) | Ours, same sunrise | Ours, our sunrise |
|---|---|---|---|
| Bhava Lagna | Makara 10°35′ | Makara 10°32′ | Makara 10°56′ |
| Hora Lagna | Karka 29°05′ | Karka 28°59′ | Karka 29°47′ |
| Ghati Lagna | Meena 24°33′ | Meena 24°19′ | Meena 26°19′ |
| Pranapada | Vrishchika 2°27′ | Vrishchika 1°31′ | Vrishchika 9°31′ |
| Varnada Lagna | Meena 0°23′ | Meena (Raman's method)Santhanam's method: Tula | |
| Sree Lagna | Dhanu 5°25′ | Dhanu 5°27′ (does not use sunrise) | |
| Indu Lagna | Karka 6°51′ | Karka 6°51′ (does not use sunrise) | |
7 July 1920, 3:32 pm, Philadelphia
| Lagna | Jagannatha Hora (published) | Ours, same sunrise | Ours, our sunrise |
|---|---|---|---|
| Bhava Lagna | Dhanu 5°31′ | Dhanu 5°28′ | Dhanu 5°51′ |
| Hora Lagna | Vrishabha 18°51′ | Vrishabha 18°44′ | Vrishabha 19°32′ |
| Ghati Lagna | Kanya 28°51′ | Kanya 28°33′ | Tula 0°33′sign changes |
| Pranapada | Vrishchika 19°17′ | Vrishchika 18°06′ | Vrishchika 26°04′ |
| Varnada Lagna | Dhanu 1°35′ | Dhanu (Raman's method) | |
| Sree Lagna | Makara 17°01′ | Makara 17°01′ (does not use sunrise) | |
| Indu Lagna | Dhanu 6°08′ | Dhanu 6°08′ (does not use sunrise) | |
With Jagannatha Hora’s own sunrise, Bhava, Hora, Sree and Indu Lagna land within a few arc-minutes of the published answer, Ghati Lagna within about a third of a degree and Pranapada within about one and a quarter degrees. Nearly all of that remaining gap comes from the 11 to 15 seconds by which its sunrise still differs from ours: at their speeds, 15 seconds of sunrise move Ghati Lagna by about 19 arc-minutes and Pranapada by about one and a quarter degrees.
The textbook arithmetic
| Source | Lagna | Published | Ours |
|---|---|---|---|
| Santhanam, Brihat Parashara Hora Shastra chapter 5 (12 ghatis 30 vighatis; Sun at sunrise 132°) | Bhava Lagna | Tula 27°00′00″ | Tula 27°00′00″ |
| Hora Lagna | Makara 12°00′00″ | Makara 12°00′00″ | |
| Ghati Lagna | Simha 27°00′00″ | Simha 27°00′00″ | |
| Santhanam, Brihat Parashara Hora Shastra chapter 3, Pranapada (985 vighatis; Sun at 15° of Mesh, Vrishabh, Mithun) | Pranapada | Tula 5°00′00″ | Tula 5°00′00″ |
| Pranapada | Karka 5°00′00″ | Karka 5°00′00″ | |
| Pranapada | Mesha 5°00′00″ | Mesha 5°00′00″ | |
| P.V.R. Narasimha Rao, examples 8–9 (766 minutes after sunrise; Sun 294°17′) | Hora Lagna | Kumbha 17°17′00″ | Kumbha 17°17′00″ |
| Ghati Lagna | Kanya 21°47′00″ | Kanya 21°47′00″ | |
| P.V.R. Narasimha Rao, example 10, Sree Lagna (Moon 13°06′ Tula, Lagna 25°05′ Kanya) | Sree Lagna | Meena 18°47′00″ | Meena 18°47′00″ |
| Published Sree Lagna lesson, 4 April 1970 (full chart from the planetary tables) | Sree Lagna | Vrishabha 5°48′32″ | Vrishabha 5°47′39″ |
These examples give the inputs directly, so they test the formula alone. Every one matches; the Sree Lagna lesson is the only full-chart case, and there the Moon’s position differs by two arc-seconds, which Sree Lagna multiplies by 27.
Why each disagreement happens
Sunrise, the biggest cause
Bhava, Hora, Ghati and Pranapada all count time from sunrise, and the Brihat Parashara Hora Shastra does not say which sunrise. The upper-edge sunrise and the disc-centre sunrise are about 1.1 to 1.4 minutes apart across India, and more at higher latitudes: 1.6 minutes at Philadelphia in July. Ghati Lagna moves about 1.25 degrees a minute and Pranapada about 5, so the choice alone can change a sign. In the 1920 chart, our upper-edge sunrise puts Ghati Lagna at the very start of Tula, where Jagannatha Hora’s disc-centre sunrise gives the end of Kanya.
Four schools of Varnada Lagna
Varnada counts the lagna and the Hora Lagna forward or backward depending on whether each is an odd or even sign, and the schools disagree on which sign’s parity sets the final direction. B.V. Raman and Jagannatha Hora follow the lagna; Santhanam follows the result; two further schools work in degrees. In the 1776 chart, Raman’s method gives Meen and Santhanam’s gives Tula.
An old Pranapada error
The text counts Pranapada in signs: one sign for every 15 vighatis, which is one sign every six minutes. Reading the same quotient as degrees makes Pranapada thirty times too slow. Our own calculator had this error until 25 October 2026; it is corrected and tested against Santhanam’s examples. A smaller split is the base: the text and Jagannatha Hora use the Sun at birth, while some calculations use the Sun at sunrise.
Sree Lagna magnifies the Moon
Sree Lagna multiplies the Moon’s progress through its 13°20′ nakshatra up to a full 360°, so any difference in the Moon’s position grows about 27 times. A different ayanamsha or set of planetary tables, or a birth time a minute off, shows up clearly in its degree.
Indu Lagna: sign, not degree
Indu Lagna is a sign, counted from the Moon by the Uttara Kalamrita. Jagannatha Hora attaches the Moon’s degree to it as a convention; an answer that gives the sign only is just as correct.
What PanchangBodh uses, and why
- Sunrise at the upper edge of the Sun, with standard refraction: the standard astronomical definition, and the one our panchang pages show. Where Jagannatha Hora’s disc-centre sunrise would give a different sign, the calculator shows that second result, labelled.
- Varnada by Raman’s method, which Jagannatha Hora also uses, with Santhanam’s reading shown as a second result whenever the sign differs.
- Pranapada in signs from the Sun at birth, as the text and Santhanam’s examples have it.
- Sree Lagna by the definition P.V.R. Narasimha Rao and Sanjay Rath teach, without calling it a rule of Parashara.
- Indu Lagna counted from the Moon, with the Moon’s degree shown and labelled as Jagannatha Hora’s convention.
- Next to every result, how many minutes earlier or later the birth time would have to be for the sign to change, so you can see how much your birth-time accuracy matters.