Choosing an Ayanamsha: Lahiri, Raman, KP and Fagan–Bradley

Two sidereal charts place the same planet at different degrees. If the date, time and zodiac choice agree, check the full ayanamsha name. “Sidereal” alone does not establish that both calculations use the same origin.

An ayanamsha defines the angular difference between the chosen sidereal origin and the tropical origin. Changing the reference can change a planet’s sidereal longitude. To reproduce a source’s example, you may need the particular version as well as a family name such as Lahiri or KP.

Hermes offers 47 built-in ayanamshas and one custom option. This guide covers the twelve entries in its Common group and four additional Lahiri/KP variants. “Common” is a menu grouping, rather than a worldwide usage ranking.

What does an ayanamsha choice change?

The Tropical and Sidereal Zodiacs guide explains what an ayanamsha is; this article focuses on choosing a particular definition. As a reminder: sidereal longitude = tropical longitude − the ayanamsha calculated for that date.

An ayanamsha is not, however, one unchanging number for every date. The definition’s reference epoch, stellar anchor and calculation model matter.

Precise calculations also involve details such as the reference plane and nutation. Nutation is a shorter-period change in the orientation of Earth’s axis. When comparing two numerical values under the same ayanamsha name, check whether that effect is included. The Swiss Ephemeris programming manual, §12.1–12.2, distinguishes the reference selection from the reported ayanamsha value.

How do the four main references differ?

Lahiri / Chitrapaksha: A reference associated with the Spica/Citra tradition. The standard Lahiri definition in Swiss Ephemeris corresponds to the definition used by the Indian Astronomical Ephemeris from 1985. The documentation separately describes the earlier ICRC definition and other Lahiri versions. Standard Lahiri should therefore not be equated with True Citra, which anchors Spica at exactly 0° Libra on each date.

Raman: A separate definition used under the name of B. V. Raman. The Swiss documentation reports that Raman identified 389 CE as the year of zero ayanamsha. Examining that technical reference does not amount to applying every method in Raman’s book or reviewing the book in detail.

Krishnamurti / KP: The basic Krishnamurti definition is distinct from VP291, which uses the equinox of 291 CE as its origin. Swiss Ephemeris documents separate references. Writing only “KP” can leave the intended calculation insufficiently specified.

Fagan–Bradley: A reference associated with the modern Western sidereal tradition. Its origin differs from standard Lahiri; sharing the label sidereal does not require the same planetary degree. Do not read the historical discussion in the Swiss documentation as establishing one certain origin used by every Babylonian record.

The technical definitions are described in Swiss Ephemeris §2.8.2, §2.8.5, §2.8.6 and §2.8.9. Consult the original text separately before deriving a school-wide rule from a particular book passage.

Is Fagan–Allen a separate option?

Hermes has one entry labelled “Fagan-Bradley / Fagan-Allen.”

Two names in this label do not add another ayanamsha to the menu. To establish whether a similar label in another program uses the same definition, compare the name, reference and output together.

The twelve entries in the Hermes Common group

The codes below provide shorthand for the entries. Record the option name, reference type and source you are trying to reproduce together.

These names have different kinds of origin. Some relate to stellar positions, some to a selected epoch, and others to a particular author’s convention. Their availability in a menu does not establish the astronomical validity of every historical or spiritual belief associated with them.

What distinguishes the four Lahiri/KP variants?

Publications using the Lahiri name can specify different starting values, which makes the source important. The detailed Swiss Ephemeris discussion of Lahiri and Krishnamurti examines the differences in definition and reference date.

Names such as “1940” or “VP285” identify a definition; they do not restrict you to calculating charts for that year. You can compare all these references on the same chart date.

Rather than choosing a version merely because it is older or newer, establish which definition the calculation you want to reproduce uses. A small discrepancy may come from the reference version rather than incorrect birth data.

What is held fixed in True Citra, True Revati and True Pushya?

These three definitions anchor a particular star to a specified sidereal longitude. The Swiss Ephemeris definitions are:

These target degrees are not the numerical ayanamsha values. In True Citra, for example, 180° describes Spica’s sidereal position; it does not mean you should subtract 180° from tropical positions.

The star’s calculated tropical position for the date is related to its target sidereal longitude to establish the reference. Because of stellar proper motion and the calculation model, propagating an initial epoch value and holding a star at its target longitude on every date are different definitions. This is an important distinction between standard Lahiri and True Citra.

Do not confuse “True” in these names with the True Node choice explained in our Lunar Nodes guide. One concerns a stellar ayanamsha reference; the other concerns the Lunar Node calculation. The stellar definitions in Swiss Ephemeris §2.8.4–2.8.5 can be read alongside the precision settings described in the programming manual, §12.2.

What can a small difference do at a sign boundary?

Choose an illustrative tropical planetary position of 24°00′ Aries. Compare two hypothetical ayanamshas:

For B, 24°00′ − 24°10′ gives −0°10′. Adding a full circle gives 359°50′, or 29°50′ Pisces. The short separation between the results is just 0°20′.

A different sign label does not necessarily mean a large separation. Equally, dismissing the difference as “only twenty minutes” can obscure a classification that crosses a boundary. Exact degrees matter when studying a sign boundary or another division.

A and B are not actual Lahiri or Raman values. This example demonstrates how one tropical position is expressed from different origins. Use the program’s calculation with the selected reference for the final sidereal position.

Compare four references in Hermes with the same data

Use the synthetic sample 20 March 2000, 12:00:00 UTC, 41° north, 29° east; Gregorian calendar. Verify the time-zone conversion for that date if the form requires local time.

1. Establish the sidereal starting chart. Use Placidus and True Node. Keep the cusp setting, transformation and coordinate view at Normal. Record the version.
2. Make the Lahiri record. Write the full ayanamsha name, numerical value if displayed, and the sidereal longitude of a chosen planet. For example, select the Sun and follow it throughout.
3. Change only the ayanamsha. Make separate records for Raman, Krishnamurti (KP) and Fagan-Bradley / Fagan-Allen. Keep the date, UTC, location and other choices fixed.
4. Examine the degree difference first. If a sign changes, measure the distance from the boundary. Record house placement separately rather than treating it as the same measurement.
5. Study the variants separately. Compare standard Lahiri with 1940/VP285/ICRC, and basic KP with VP291. Keep this version comparison separate from the initial four-reference table.

To investigate the date dependence, repeat the study in a separate dataset for 20 March 1900, 12:00 UTC. Specify the Gregorian calendar for that date too. Compare references within each date before comparing dates; subtracting Lahiri in 1900 from Raman in 2000 does not isolate a difference between methods.

For a precise comparison between programs, also record the ephemeris version, reference plane and nutation convention. If the interface does not expose a detail, mark it unknown. The same ayanamsha name does not establish that every technical choice matches.

Does selecting an ayanamsha select a complete school of astrology?

An ayanamsha sets a zodiac reference. The house system, Lunar Node calculation and techniques used are separate choices. Selecting a KP ayanamsha alone does not establish that sub-lord or every other stellar technique has been applied. Similarly, selecting Lahiri does not prescribe one house method for every Jyotish source.

When following a lesson or book, record its full ayanamsha definition alongside the other settings. If the version behind “Lahiri” is unclear, preserve that uncertainty as a question to resolve.

See the Hermes Chart Settings guide for saving preferences and setting new-chart defaults. A record such as “Sidereal · Lahiri ICRC · Placidus · True Node · specified UTC” gives you a much clearer basis for reproducing the result.