6e0f4a679c
Replaces the original JS calibration library with a pure Python pipeline for collecting and back-calculating solar depression angles from human-verified Fajr and Isha prayer sightings. What this does: - src/pipeline.py: master pipeline; fetches iCal + manual records, back-calculates angles via PyEphem, applies quality filters, exports two clean CSVs - src/collect/openfajr.py: parses the OpenFajr Birmingham iCal feed (~4,018 records) - src/collect/verified_sightings.py: manually compiled records from peer-reviewed studies (Egypt, Saudi Arabia, Malaysia, Indonesia, UK, USA, Canada, and more) - src/angle_calc.py: PyEphem back-calculation with atmospheric refraction - src/elevation.py: Open-Elevation API batch lookup Datasets generated: - data/processed/fajr_angles.csv: 4,105 confirmed Fajr records, 35 locations, latitude range -37.8 to 53.7 degrees, date range 1985-2026 - data/processed/isha_angles.csv: 43 confirmed Isha records, 20+ locations Also includes: - notebooks/01_exploratory_analysis.ipynb: latitude, TOY, elevation pattern analysis - research/: academic paper summaries (not training data) - data/raw/sources.md: full citation table for all data sources
3 KiB
Malaysia and Indonesia Studies
Kassim Bahali et al. 2018 (DSLR Study)
Paper: Kassim Bahali, N.F., et al. "Determination of Fajr and Isha prayer times based on astronomical observation at low latitude." Sains Malaysia, 47(11): 2797-2805, 2018.
Location: Kuala Lumpur and surrounding Malaysia/Indonesia sites (2°N-7°S range) Method: DSLR astrophotography + SQM (Sky Quality Meter) sky brightness Data: 64 observation days, February-December 2017
Key result: Mean Fajr depression = 16.67° (range 13.9°-19.8°)
The DSLR + SQM combination is methodologically stronger than naked-eye only. The SQM provides an objective measure of sky brightness that eliminates observer subjectivity. At near-equatorial latitudes (2°-7°), the Sun rises and sets at a steep angle through the horizon, producing very short, sharp twilight transitions.
Saksono 2020 (Depok, Indonesia)
Paper: Saksono, T. "Fajr prayer time determination using the Sky Quality Meter." NRIAG Journal of Astronomy and Geophysics, 9(1): 238-244, 2020.
Location: Depok, West Java, Indonesia (6.4°S, 106.83°E, 65m) Method: SQM sky brightness monitoring; 26 nights June-July 2015 Result: ~16° mean Fajr depression
Hamidi 2007-2008 (Malaysia Isha Study)
Source: Zety Sharizat Hamidi, Determination of Isha prayer time based on shafaq abyad in Malaysia. Academia.edu, 2008.
Location: Two sites:
- Kuala Lipis: 4.183°N, 102.040°E, 76m (east coast)
- Port Klang: 3.004°N, 101.403°E, 5m (west coast)
Method: Naked-eye observation of Shafaq al-Abyad disappearance; May 2007 - April 2008 Result: Isha (Shafaq Abyad) consistently at approximately 16°-17° depression
OIF UMSU (Medan, North Sumatra 2017-2020)
Location: OIF (Observatory of Islamic Fajr) at University of Muhammadiyah North Sumatra, Medan (3.595°N, 98.672°E, 22m) Method: SQM photometry; hundreds of observation days Proposed angle: 16.48° for Indonesian national standard
Key Pattern: Equatorial Sites Yield Higher Angles
All Malaysia/Indonesia studies find Fajr at ~16°-17°, compared to ~13°-14° in Birmingham and the UK. This is a systematic and significant pattern:
| Latitude | Representative Site | Mean Fajr Angle |
|---|---|---|
| 52°N | Birmingham, UK | ~13° |
| 40°N | Ankara, Turkey | ~15° |
| 30°N | Egypt (desert) | ~13.5°-14.5° |
| 27°N | Hail, Saudi Arabia (1020m) | ~14.4° |
| 3°-7°N | Malaysia/Indonesia | ~16°-17° |
| 3°-7°S | Indonesia (Java) | ~16°-17° |
| 33°-37°S | Cape Town / Auckland | ~15°-16° |
This counter-intuitive result (equatorial sites have higher angles than mid-latitude sites) is likely caused by the geometry of the Earth's atmosphere: at equatorial latitudes, the Sun rises at a steeper angle through the horizon, so morning twilight is briefer and more intense. The same absolute angle corresponds to a later moment relative to sunrise at lower latitudes.
The ML model should capture this latitude-dependent pattern.