Nine-graha sidereal positions

gochara.graha-positions

Sidereal longitude produces rashi, Nakshatra, Pada, retrograde state, and next ingress for nine grahas.

Assurance

Level	Current statement
Documented and traceable	Yes — the canonical record includes the process and a worked example.
Regression or reproduction checked	Linked to 1 repository test file(s).
Independently source-supported	Partial support only; read the provenance note and limitations before generalizing.

Computation method

Method type: algorithm

Compute sidereal longitude and speed for each of nine Grahas, derive the categorical fields, and search adaptively for the next 30-degree sign crossing.

Process

1. Set the requested Swiss Ephemeris sidereal mode.
2. Compute longitude and daily speed; derive Ketu as mean Rahu plus 180 degrees.
3. Map longitude to Rashi, one of 27 Nakshatras, and one of four Padas; mark negative speed as retrograde.
4. Step adaptively toward the nearest sign boundary and bisect the first sign-index change with 40 iterations.
5. Convert the ingress to an IST date, emit the next Rashi, and restore Lahiri mode.

Formulae

Rashi, Nakshatra, and Pada

r=floor(lambda/30); n=floor(lambda/(360/27)); pada=(floor((lambda/(360/27))*4) mod 4)+1

• lambda: normalized sidereal longitude in degrees

Worked example

Guru at Hyderabad sunrise, 2026-06-11

Inputs

• UT Julian day: 2461202.5077662035
• Ayanamsa: Lahiri

Calculation

1. Guru longitude = 91.7834 degrees, placing it in Rashi index 3 and Punarvasu Pada 4.
2. Positive daily speed means it is not retrograde.
3. The next sign-index crossing is searched numerically.

Result

• Rashi: Karka
• Nakshatra: Punarvasu, Pada 4
• Next Rashi: Simha on 2026-10-31 IST

Method notes

• The longitude evidence boundary is inherited from the Drik calculation; next-ingress date localization is currently fixed to IST.

Contract

Owning layer: calendar
Claim kind: deterministic-fact
Time basis: Requested Julian day, normally local sunrise for daily surfaces.

Inputs

• Julian day
• ayanamsa

Outputs

• longitude
• rashi
• Nakshatra
• Pada
• retrograde
• next ingress date

References and evidence

Evidence classes: astronomical
Verification states: partially_verified

The same Drik longitude evidence boundary applies to these derived fields.

drik.sidereal_positions

Evidence class: astronomical
Verification state: partially_verified
Locator: Swiss Ephemeris Programmer's Documentation sections 3, 5.8 and 12.2 for calc_ut, sidereal flags and ayanamsa modes; representative date checks in tests/test_drik_engine.py and tests/test_ayanamsa.py
Last reviewed: 2026-08-27
Scope: Traces the Drik longitude API and preserves representative outputs. The current register does not contain an exhaustive independently published position-and-transition fixture, and it establishes no interpretive doctrine.

Sources

• Swiss Ephemeris — Astrodienst; Swiss Ephemeris 2.10 Programmer's Documentation and pyswisseph runtime used by the repository; authority type: astronomical_reference
• Drik Panchang day and festival pages — Drik Panchang; Location- and date-specific web pages; authority type: published_panchangam

The complete machine-readable source registry is available in provenance.json. A regression fixture or same-code reproduction is not independent verification.

Reproduce and review

• tests/test_graha_positions.py

Run the linked tests, then the complete offline contract:

python tools/verify_project.py

Public surfaces

• python-library
• mcp
• website
• generated-data

Limitations

• Rahu and Ketu use the selected node convention; next-ingress dates are numerical search results and rasi_until is currently rendered as an IST calendar date rather than the requested city's local date.

Implementation

• owner: telugu_panchangam/gochara/positions.py — graha_positions

This route is generated from computations.json. Edit the registry and canonical reference prose in the same pull request as a behavior change.