Trikona and JHora: where the numbers can differ, and why
Trikona and Jagannātha Horā (JHora) make some different calculation choices. Most are conventions: each program follows a rule, just a different one. This page lists each one, how it shows up on a chart, and the Trikona setting that matches JHora where there is one.
Each item says how far it has been checked: Checked in JHora 8.0 (read from the JHora 8.0 desktop program), Compared with PyJHora, not JHora (PyJHora is an open-source program modelled on JHora; agreeing with it does not prove agreement with JHora), or Not checked against JHora.
Calculations verified against Swiss Ephemeris on 25,000 charts. The comparison with JHora 8.0 covers 20 charts for combustion and 50 charts for positions, vargas, nakṣatras, panchāṅga and Viṁśottarī dates.
Ayanāṁśa (Lahiri)
What differs. Trikona's Lahiri is the standard modern definition, the one Swiss Ephemeris uses: 22°27′37.84″ at 1900, carried forward with the IAU 2006 precession model. JHora 8.0 calls the same zero point Traditional Lahiri: across the 50 charts from 1900 to 2027 the two were 0.14″ apart. JHora's default is a different option, True Lahiri/Chitrapaksha, which keeps the star Citrā (Spica) at 180°.
How it shows up. With JHora left at its default, the two ayanāṁśas are 52″ to 58″ apart, about one arcminute: 52″ for a 1900 birth, 57″ for 2018, 58″ for 2027; the gap changes slowly with the birth year. Trikona's planets, Rahu and Ketu therefore sit about 52″ to 58″ behind JHora's. The Moon can be up to about 64″ behind, because of the timing difference for births from 2020 on, and the lagna about 37″ to 74″ behind, because of the nutation difference (both below). In the 50 charts at the two defaults it changed 2 rāśi signs (a Moon and a lagna that sat within half a minute of a cusp), one Moon pada, one lagna pada, 6 navāṁśa signs and 6 daśāṁśa signs out of 500 placements, and, with both dropping the seconds, 457 of 500 positions showed a different minute. Mahādaśā start dates differed by a median of 6 days and at most 11 days. With JHora on Traditional Lahiri, no sign or pada changed, 484 of 500 positions showed the same minute (the other 16 sat within 17″ of a minute edge; see how positions are shown on screen, below), and the daśā difference falls to the daśā-year difference below.
Why. An ayanāṁśa is a convention, not a measured quantity, and programs define the same name differently.
Trikona setting. To match: in JHora choose Preferences → Related to Calculations → Ayanamsa → Traditional Lahiri, and keep Trikona on Lahiri, its default. To match JHora's default instead, set Trikona to Ayanāṁśa: True Citrā, whose ayanāṁśa agreed with JHora's True Lahiri/Chitrapaksha to within 0.03″ on the 50 charts.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. Compared: all ten positions (lagna, the seven planets, Rahu, Ketu), navāṁśa, daśāṁśa, nakṣatra, tithi, yoga, karaṇa, vāra and Viṁśottarī dates.
Rahu and Ketu: mean or true node
What differs. Trikona uses the mean node by default, as JHora 8.0 does. The true node swings around it.
How it shows up. With the true node, Rahu and Ketu move by up to about 1.8° from the mean position, and can change nakṣatra or, near a sign edge, sign. With the same ayanāṁśa and both programs on the mean node, Rahu and Ketu differed by less than 0.25″ on all 50 charts. Switching Trikona to the true node changed the navāṁśa of 28 and the rāśi of 2 of the 100 node placements.
Why. Classical texts treat the nodes as calculated points and give no model of the wobble; the mean node is the long-standing Pārāśarī convention.
Trikona setting. Settings, Defaults, Advanced options, Node type: Mean (default) or True.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. JHora 8.0 uses mean nodes on a fresh install. PyJHora, by contrast, defaults to the true node.
Planet positions: true or apparent
What differs. Trikona charts use true (geometric) positions: no light-time or aberration correction. JHora 8.0 also uses true positions by default. Many astronomy programs use apparent positions.
How it shows up. With apparent positions the Sun moves by about 20″, and a slow planet's sign change moves by up to about an hour and a half (see the 2027 calendar). With the ayanāṁśa matched, Trikona's and JHora 8.0's planets agreed within 1″ for births up to 2018.
Why. JHora 8.0 uses true positions by default, and the siddhāntic true planet (spaṣṭa) also has no light-time or aberration correction.
Trikona setting. No setting; Trikona charts always use true positions.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. JHora 8.0's defaults on a fresh install: geocentric, true positions; the annual aberration and light-deflection boxes are ticked but apply only to apparent positions, so they do not change the chart; refraction off; nutation on.
Births from 2020 on
What differs. For births from 2020 on, JHora 8.0 places every planet slightly further along than Trikona, as if the birth were a few seconds later: about 3 seconds for 2020, 9 to 10 for 2024 and 13 for 2027.
How it shows up. The Moon moves most, by up to about 7″ for a 2027 birth; the Sun by under 1″. This can change a sign or nakṣatra only for a Moon within a few arcseconds of an edge.
Why. Most likely the length of the day: JHora 8.0 dates from 2016 and uses a forecast of how Earth's rotation would slow in later years, while Trikona uses the measured values, and Earth slowed less than forecast. This is our reading of the numbers, not something seen in JHora's code.
Trikona setting. No setting.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. Seen on the charts from 2020, 2024 and 2027; the cause is inferred.
Lagna and nutation
What differs. With the same ayanāṁśa, Trikona's lagna and JHora 8.0's differ by the nutation of the equinox, a small periodic wobble of Earth's axis. JHora removes nutation from the planets but keeps it in the lagna; Trikona removes it from both.
How it shows up. The lagna differs by up to about 19″, ahead or behind depending on the date, so its last minute can read 1′ different. It changes the lagna's sign or nakṣatra only within 19″ of an edge; none changed in the 50 charts.
Why. Trikona measures the lagna and the planets from the same reference; JHora 8.0 uses a different one for the lagna.
Trikona setting. No setting.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. On every chart the lagna difference equals the nutation, to 0.01″.
How positions are shown on screen
What differs. Trikona shows degrees and minutes and drops the seconds, as JHora's degree-minute-second reading does. JHora also shows the seconds.
How it shows up. A planet at 10°05′40″ shows as 10°05′, the same minute JHora prints. With JHora on Traditional Lahiri, 484 of 500 positions in our 50-chart test showed the same minute; the other 16 sat within 17 seconds of a minute edge.
Why. Minutes keep the chart readable on a phone.
Trikona setting. None needed; compare JHora's degrees and minutes and ignore its seconds.
Checked in JHora 8.0. JHora 8.0's longitude panel shows hundredths of a second; Trikona's minute display is in its chart code.
Combustion (asta)
What differs. Trikona decides combustion with the Sūrya-Siddhānta IX.16 kālāṁśa rule, which converts the classical distance in time to a distance along the zodiac for each sign.
How it shows up. An earlier fixed-degree rule in Trikona disagreed with JHora 8.0 on 17 of 100 planet readings across 20 charts; each time Trikona said combust and JHora did not. The current rule has not yet been compared with JHora.
Why. The kālāṁśa rule is the text's own method.
Trikona setting. No setting.
Checked in JHora 8.0. The 20-chart comparison used the earlier rule. A new comparison with the current rule is pending.
Sunrise
What differs. Trikona takes sunrise when the centre of the Sun's disc reaches the horizon, without atmospheric refraction.
How it shows up. Almanacs that use the Sun's upper edge with refraction give sunrise a few minutes earlier, which moves the first horā and other sunrise-based times.
Why. Trikona follows JHora 8.0's default; the classical texts do not settle it.
Trikona setting. No setting.
Checked in JHora 8.0. JHora 8.0's sunrise setting on a fresh install: the centre of the Sun's disc on the horizon, refraction off. In the 50-chart check, 11 births were before sunrise, and both programs gave the previous day's vāra for all 11. Sunrise times themselves were not read from JHora.
Karaṇa at Amāvāsyā
What differs. For the four fixed karaṇas Trikona follows the order in Sūrya-Siddhānta II.67: Śakuni, Nāga, Catuṣpada, Kiṃstughna. Many modern pañcāṅgas swap Nāga and Catuṣpada, and JHora 8.0 showed the swapped name in the one case checked.
How it shows up. In the first half of Amāvāsyā, the one case in the 50 charts, JHora showed Catuṣpada and Trikona Nāga, for the same moment and the same tithi. By each program's order the second half would then read Catuṣpada in Trikona and Nāga in JHora; that half was not seen in the check. Only these two of the 60 half-tithis are affected.
Why. Trikona keeps the text's order; much of current practice uses the other one.
Trikona setting. No setting.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. One chart fell in the first half of Amāvāsyā, where JHora showed Catuṣpada and Trikona Nāga; the second half did not occur in the 50 charts. The karaṇa agreed on the other 49 charts.
Bhāva (house) cusps
What differs. Trikona's default is whole-sign houses. It also offers Equal, Śrīpati, Bhāva Chalit, Placidus and KP. Trikona's Śrīpati divides each quadrant in three, with the cusp as the start of the bhāva.
How it shows up. If your JHora charts show Śrīpati bhāvas and Trikona is on whole sign, planets near a sign edge can sit in different houses.
Why. Different schools use different bhāva divisions.
Trikona setting. Settings, Defaults, House system.
Not checked against JHora. Whether JHora's bhāva table matches Trikona's Śrīpati cusps on the same chart has not been compared.
Daśā year length
What differs. New Trikona charts count daśā years as 365.25 days (Julian). The other choices are the sidereal year, 365.25636 days, and Sun's return: a daśā year is the Sun's return to the same sidereal degree, which is JHora 8.0's default (its "true sidereal solar year"). Under Sun's return the years vary slightly in length and follow the Sun's faster motion in January.
How it shows up. Julian and sidereal years move daśā dates apart by up to about 18 hours over the full 120-year Viṁśottarī cycle. Against JHora 8.0, with the ayanāṁśa matched, those fixed years put mahādaśā starts a median of about 1 day and at most 4.4 days from JHora's in the 50 charts. With Sun's return, the year rule itself agreed with JHora's to within 3 minutes, and mahādaśā starts were a median of about 20 minutes and at most about 105 minutes from JHora's for births up to 2018. The rest comes from the Moon: a daśā start moves with the Moon's degree, and even the 0.14″ between the two Lahiris moves it by tens of minutes. For births from 2020 on, the Moon's timing difference (see above) adds up to about 7 hours.
Why. Schools disagree on the year used for daśā periods.
Trikona setting. Settings, Defaults, Advanced options, Daśā year length: Julian (default), Sidereal, or Sun's return (JHora default). Choose Sun's return to follow JHora's year.
Checked in JHora 8.0. On 50 made-up charts (1900 to 2027, 44 cities, 14 in daylight saving), under JHora's default settings and under Traditional Lahiri. JHora 8.0's default "Definition of year in dasas" is "True sidereal solar year".
Marriage matching: Gaṇa and Vaśya tables
What differs. Trikona reads the Gaṇa and Vaśya tables with the groom's row and the bride's column. For Gaṇa this follows B. V. Raman's Muhurtha; for Vaśya, Muhūrta Chintāmaṇi (Vivāha-prakaraṇa 23, with Mahīdhara's commentary). Trikona assigns Vaśya groups by whole sign. PyJHora reads both tables the other way round.
How it shows up. For uneven pairs the points swap: a Rākṣasa groom with a Deva bride gets 1 Gaṇa point in Trikona and 0 in PyJHora; a Deva groom with a Manuṣya bride gets 6 in Trikona and 5 in PyJHora.
Why. Raman gives the Gaṇa point to the groom's side in these pairs, and Muhūrta Chintāmaṇi gives the Vaśya points when the bride's sign is vaśya to the groom's, not the reverse. Muhūrta Chintāmaṇi's Gaṇa verse (Vivāha-prakaraṇa 30) states the pairs without saying which side is the groom's.
Trikona setting. No setting.
Compared with PyJHora, not JHora. JHora 8.0's matching screen has not been compared.
Found a difference that is not listed?
Email support@trikona.app with the setting names you use in JHora and the first number that differs. Please do not send a client's birth details; a made-up birth time that shows the difference is enough.
Related pages
- Importing JHora .jhd files: what carries over
- Trikona and Jagannātha Horā compared
- Sidereal calendar 2027
- How Trikona works
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Why does Trikona show a slightly different degree from JHora?
Most often the ayanāṁśa. JHora's default, True Lahiri/Chitrapaksha, sits 52″ to 58″ from Trikona's Lahiri, depending on the birth year. Set JHora to Traditional Lahiri and the planets agree within a second of arc for births up to 2018. A position within a few seconds of a minute edge can still read 1′ different.
Can I make Trikona match JHora?
Mostly. Put JHora on Traditional Lahiri (Preferences → Related to Calculations → Ayanamsa) with mean nodes, its default; keep Trikona on Lahiri and set its Daśā year length to Sun's return. In our 50-chart check every rāśi, navāṁśa, daśāṁśa, nakṣatra, tithi, yoga and vāra then agreed. Four differences remain: the lagna (up to about 19″, nutation), Viṁśottarī dates (a median of about 20 minutes and at most about 105 minutes for births up to 2018, from the Moon's position), planets in births from 2020 on (the Moon by up to about 7″), and the karaṇa name at Amāvāsyā, where Trikona follows Sūrya-Siddhānta's order (seen in the first half; the second half follows from the two orders).
Has every Trikona result been compared with JHora?
No. Each row on this page says what was checked in JHora 8.0. The 50-chart comparison covered positions, vargas, nakṣatras, panchāṅga and Viṁśottarī dates; house cusps, combustion under the current rule, marriage matching and sunrise times are not yet compared.