Sidereal Vedic astrology requires choosing an ayanamsa, the offset that converts a tropical zodiac longitude into a sidereal one. The two main contenders in contemporary Vedic practice are Lahiri Chitrapaksha (the Indian government's official ayanamsa, anchored to the star Spica) and True Pushya Paksha (the alternative championed by P V R Narasimha Rao, anchored to the centre of the Pushya nakshatra). The two systems differ by approximately 0.10 degrees in 2026, a small amount in absolute terms but operationally significant for several categories of chart reading.
Tempora's framework uses True Pushya Paksha as the calibration anchor. This article walks through what each ayanamsa is, what the PVRN Rao argument is, where the two systems diverge in practice, and why Tempora picked Pushya Paksha. The choice is a methodological commitment, not a claim that Lahiri is wrong.
What ayanamsa is, mechanically
The tropical zodiac is anchored to the vernal equinox, the moment in spring when the Sun crosses the celestial equator northward. Tropical 0 degrees Aries is defined as the position of the Sun at the spring equinox. The tropical zodiac is the system Western astrology uses.
The sidereal zodiac is anchored to the fixed stars. Sidereal 0 degrees Aries is defined relative to a specific star or stellar region, not to the equinox. The sidereal zodiac is the system Vedic astrology uses.
The two zodiacs are misaligned because of precession of the equinoxes, the slow wobble of Earth's rotation axis that shifts the equinox position against the fixed stars by approximately 50 arc-seconds per year. Over centuries this shift accumulates into a degree-scale offset between the two zodiacs. The offset in 2026 is approximately 24 degrees.
The ayanamsa is the numerical value of this offset, used to convert tropical longitudes (which Swiss Ephemeris and other astronomical libraries compute directly) into sidereal longitudes for Vedic analysis. The choice of ayanamsa is the choice of which specific anchor star defines sidereal 0 degrees Aries.
Lahiri Chitrapaksha: the government standard
Lahiri Chitrapaksha is the ayanamsa adopted by the Indian government's Calendar Reform Committee in 1955 under the chairmanship of N C Lahiri. The committee was charged with rationalising the multiple Indian almanac traditions into a single official reference, and the ayanamsa choice was central to that work.
The system anchors the sidereal zodiac to the bright star Spica (called Chitra in Sanskrit) at exactly 0 degrees Libra sidereal. The choice of Spica as the anchor reflects the classical tradition where Chitra is named as the anchor in several Sanskrit astronomical texts. The Lahiri implementation uses a mean-precession approximation that gives a stable secular trend in the ayanamsa value over centuries.
The ayanamsa value in 2026 is approximately 24.20 degrees. Lahiri Chitrapaksha is the default in most contemporary Vedic astrology software (Jagannatha Hora, Parashara's Light, AstroSage, the Indian National Calendar), and it is the most widely-used Vedic ayanamsa in modern practice. The government-of-India endorsement and the south Indian school's adoption have made Lahiri the de facto standard for most English-language Vedic astrology.
True Pushya Paksha: the PVRN Rao alternative
True Pushya Paksha is the ayanamsa championed by P V R Narasimha Rao (commonly abbreviated PVRN Rao), the author of Jagannatha Hora and an active researcher in the Vedic computational tradition. The system anchors the sidereal zodiac to the star delta Cancri at the centre of the Pushya nakshatra.
The PVRN Rao argument for the Pushya anchor proceeds along three lines. First, the Pushya nakshatra is structurally central in the Vedic nakshatra system (the 8th of 27 nakshatras, anchoring the zodiac roughly at the centre), and choosing a central anchor minimises the cumulative drift of nakshatra positions over time. Second, the actual stars in the Pushya cluster are relatively dense and the centre of the nakshatra is well-defined astronomically, which makes the anchor reproducible without large interpretive choices. Third, several classical authority-figure birth chart computations align more cleanly with the Pushya anchor than with the Spica anchor, which PVRN Rao reads as evidence of the framework's better fit with the classical tradition.
The system is called 'True' Pushya Paksha because it uses the actual current position of the anchor star computed for each date rather than a mean-precession approximation. The 'True' qualifier distinguishes it from a simpler approximation that uses a long-term average precession rate without correcting for short-term irregularities in Earth's axis motion. The True implementation is more astronomically accurate but requires the Swiss Ephemeris computation layer to deliver the date-accurate ayanamsa value.
The ayanamsa value in 2026 is approximately 24.10 degrees, about 0.10 degrees less than Lahiri Chitrapaksha. The Pushya Paksha implementation is shipped with PVRN Rao's open-source Jagannatha Hora software and is supported in Swiss Ephemeris as a named ayanamsa option.
How the 0.10-degree difference plays out in practice
In absolute terms, 0.10 degrees is small. A degree of arc corresponds to roughly two days of Sun motion or about 2 hours of Moon motion. A 0.10-degree shift moves the Sun by about 5 hours or the Moon by about 10 minutes. For most planet positions and most chart features, the shift is operationally invisible.
Three cases where the shift is operationally significant.
Nakshatra-boundary cases. A nakshatra is 13.33 degrees wide (360 degrees divided by 27 nakshatras), and the boundaries between nakshatras are fixed sidereal points. A planet near a nakshatra boundary may sit clearly inside one nakshatra under Lahiri and clearly inside the adjacent nakshatra under Pushya Paksha. The 0.10-degree shift is 0.75% of a nakshatra width, but for boundary-adjacent placements that 0.75% can be decisive. The reading of the chart can shift substantially because the nakshatra system determines the dasha-balance computation and several classical chart-interpretation rules.
Dasha-balance computations. The Vimshottari dasha system computes the native's elapsed time within the opening dasha from the natal Moon's longitude within its nakshatra. A small shift in the Moon's sidereal longitude produces a proportional shift in the dasha-balance. For a natal Moon close to a nakshatra boundary, the 0.10-degree ayanamsa difference can shift the dasha-balance by months or years over the 120-year Vimshottari cycle. The compound effect is large for charts where the Moon is boundary-positioned.
Orb-boundary signature firings. Tempora's calibrated signatures fire when a transit reaches a defined orb from a natal point (typically 4 to 8 degrees applying). A transit positioned at the orb boundary for one ayanamsa may sit just inside the orb under that ayanamsa and just outside the orb under the other. The signature fires under one system and misses under the other for the same astronomical moment. This case is rare but it exists, and the framework's calibration must commit to one system to read consistently.
Why Tempora picked True Pushya Paksha
Tempora's framework anchors on True Pushya Paksha for three structural reasons.
Calibration consistency. The calibrated lift table is built on Vimshottari dasha alignment, which depends on nakshatra positions, which depend on the ayanamsa. The corpus was computed with True Pushya Paksha fixed, and the calibrated weights against the Monte Carlo baseline reference Pushya Paksha nakshatra placements. Switching to Lahiri would require re-running the calibration on every event in the corpus, which has not been done. The framework's calibrated weights are Pushya-anchored by construction.
PVRN Rao methodological argument. The Pushya-anchor argument is technically credible. The Pushya nakshatra is centrally positioned in the 27-nakshatra system, the anchor star delta Cancri is in a relatively dense stellar region with a well-defined centre, and the True implementation uses date-accurate precession rather than mean-precession approximation. These are the kinds of choices the framework rewards: more astronomically accurate, more reproducible, less interpretively contingent.
Open-source reproducibility. PVRN Rao's Jagannatha Hora software is open source and the Pushya Paksha implementation is documented and reproducible. Anyone can verify the ayanamsa value Tempora uses against the published reference. The Lahiri implementation in most commercial software is also reproducible, but the open-source provenance of Pushya Paksha through Jagannatha Hora makes external verification more direct.
None of these reasons argues that Lahiri is empirically wrong. The two systems are both internally consistent, both produce coherent chart readings, and both have substantial classical and contemporary practitioner support. The choice between them is methodological commitment, not empirical victory. Tempora committed to Pushya Paksha at the start of the calibration project and the commitment is documented across the framework.
Can the same chart be read in both systems?
Yes. The same birth data produces a chart in each ayanamsa, and for most charts the two readings produce convergent results. The 0.10-degree shift does not move planets across major boundaries (sign or major-house cusp) except in edge cases where a planet sits within roughly 0.10 degrees of such a boundary.
For charts where one or more planets sit close to a nakshatra boundary, a major-house cusp, or an orb boundary for a calibrated signature, the two readings can diverge. The divergence is itself diagnostic. If a chart's central reading is robust under both systems, the conclusion is stable across the ayanamsa choice. If the central reading depends on which ayanamsa is chosen, the chart is sitting on a boundary that makes the reading inherently less certain regardless of which system is committed to.
Tempora's framework documents the ayanamsa sensitivity case-by-case where it matters. For a forward call that depends on a nakshatra-boundary placement, the article notes the dependency and the call's robustness to ayanamsa choice. For the broader analytical reading where the placements are not boundary-adjacent, the ayanamsa commitment operates in the background and the reading is the same under either system to several decimal places of precision.
Why this is the framework's most-important methodological choice
Of all the structural choices in a Vedic astrology framework (ayanamsa, house system, dasha system, divisional chart conventions, aspect conventions), the ayanamsa choice has the broadest downstream effect. It determines every planet's sidereal position in every chart, which determines every nakshatra placement, which determines every dasha-balance, which determines every dasha-period boundary, which determines every reading anchored on dasha timing.
House system and dasha system are also fundamental, but house-system choices can be evaluated chart-by-chart (Whole Sign and Placidus give substantially different results for the same chart and the reading can be cross-checked). Dasha system choices add a second timing layer that runs alongside the primary system. Ayanamsa is the bottom layer that everything sits on. A change at this layer cascades through the entire framework.
Tempora's commitment to True Pushya Paksha is therefore the framework's most consequential methodological choice. It is documented, it is fixed across the calibration, and it is reproducible against PVRN Rao's open-source reference. The choice is not the framework's claim to empirical superiority over Lahiri. The choice is the framework's commitment to a specific anchoring that the entire calibration is built on.
Frequently asked questions
What is an ayanamsa in Vedic astrology?
An ayanamsa is the offset between the tropical zodiac (anchored to the vernal equinox, used in Western astrology) and the sidereal zodiac (anchored to the fixed stars, used in Vedic astrology). The two zodiacs are misaligned because of precession of the equinoxes, the slow wobble of Earth's rotation axis that shifts the equinox position against the fixed stars by approximately 50 arc-seconds per year. In 2026 the ayanamsa is approximately 24 degrees, meaning a sidereal Vedic chart shows planet positions about 24 degrees earlier than a tropical Western chart for the same birth data. Different sidereal anchors give slightly different ayanamsa values, which is why multiple ayanamsa systems exist.
What is Lahiri Chitrapaksha ayanamsa?
Lahiri Chitrapaksha is the ayanamsa adopted by the Indian government's calendar reform committee under N C Lahiri in 1955. The system anchors the sidereal zodiac to the star Spica (Chitra in Sanskrit) at exactly 0 degrees Libra sidereal. The ayanamsa value is approximately 24.20 degrees in 2026. Lahiri is the official ayanamsa for the Indian National Calendar and is the default in most contemporary Vedic astrology software. The Lahiri framework is the most widely-used Vedic ayanamsa in modern practice, particularly among south Indian schools and government-aligned almanac publishers.
What is True Pushya Paksha ayanamsa?
True Pushya Paksha is the ayanamsa championed by P V R Narasimha Rao (PVRN Rao), the author of Jyotish-grade open-source Vedic astrology software and an active researcher in the Vedic computational tradition. The system anchors the sidereal zodiac to the star delta Cancri at the centre of the Pushya nakshatra. The ayanamsa value is approximately 24.10 degrees in 2026, about 0.10 degrees less than Lahiri. The system is called 'True' Pushya Paksha because it uses the actual current position of the anchor star computed for each date rather than a mean-precession approximation, giving date-accurate ayanamsa values across the calibration range.
Why does the ayanamsa choice matter?
The ayanamsa choice changes the sidereal position of every planet in every chart. In absolute terms the difference between Lahiri and True Pushya Paksha is small (about 0.10 degrees in 2026, or roughly 6 arc-minutes), but the operational consequences are significant for three cases. First, nakshatra-boundary cases where a planet near the boundary between two nakshatras may sit in one nakshatra under Lahiri and in the adjacent nakshatra under Pushya Paksha. Second, dasha-balance calculations that depend on the natal Moon's position within its nakshatra, where the small ayanamsa shift compounds into a difference of several months or years in computed dasha boundaries. Third, transit-orb signature firings where a 4-degree orb signature can fire under one ayanamsa and miss under the other for a transit near the orb boundary.
Why did Tempora pick True Pushya Paksha rather than Lahiri?
Tempora picked True Pushya Paksha for three reasons. First, the Pushya-anchored framework aligns the nakshatra boundaries with the dasha system Tempora calibrates against; the calibration was run with this ayanamsa fixed and switching would require re-running the entire calibration corpus. Second, the PVRN Rao methodological argument that the Pushya nakshatra is the most stable anchor for sidereal alignment (since Pushya is a relatively dense star cluster and the centre of the nakshatra is well-defined) is technically credible and the implementation in PVRN Rao's open-source Jyotish software is reproducible. Third, Pushya Paksha aligns more cleanly with several classical authority-figure birth chart computations that Tempora's calibration corpus uses as ground-truth event datasets. The choice is a methodological commitment, not a claim that Lahiri is wrong.
Can the same chart be read in both Lahiri and Pushya Paksha?
Yes, the same birth data produces a chart in each ayanamsa system. For most charts the two readings produce convergent results because the 0.10-degree difference doesn't shift planets across major boundaries (sign or major-house cusp). For charts where one or more planets sit close to a nakshatra boundary, a major-house cusp, or an orb boundary for a calibrated signature, the two readings can diverge. The divergence is itself diagnostic: if a chart's central reading is robust under both systems, the conclusion is stable. If the central reading depends on which ayanamsa is chosen, the chart is sitting on a boundary that makes the reading inherently less certain. Tempora's framework documents this sensitivity case-by-case where it matters.
Read next
- Swiss Ephemeris and Vedic accuracy · the computation layer beneath the ayanamsa choice
- Nakshatra strength comparison · how nakshatra positions modulate readings
- Moon nakshatra prediction · the dasha-balance computation that depends on nakshatra position
- Calibrated lift astrology · the methodology built on the ayanamsa choice
- United States, November 2029: a three-signal convergence on the Gemini stellium.
This article represents conventional Vedic teaching and Tempora Research method documentation. It does not constitute financial, legal or professional advice. Internal audit log maintained.