mirror of https://github.com/acamarata/pray-calc-ml.git synced 2026-06-30 19:04:26 +00:00

Aric Camarata 6e0f4a679c Rebuild as Python data science project

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

2026-02-25 19:32:47 -05:00

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NRIAG Egypt Studies: 1984-2014

Summary

The National Research Institute of Astronomy and Geophysics (NRIAG, Egypt) conducted the most extensive body of peer-reviewed naked-eye Fajr observations anywhere in the world. Multiple campaigns from 1984 to 2014 covered six Egyptian sites across a wide range of latitudes, elevations, and atmospheric conditions.

Key Paper

Hassan, A.H., et al. "Astronomical determination of the proper time for Fajr prayer." NRIAG Journal of Astronomy and Geophysics, 3(1): 23-26, 2014. DOI: S2090997714000054

Sites and Findings

Site	Lat/Lng	Elevation	Years	Mean Fajr Angle	Conditions
Kottamia Observatory	30.03°N, 31.83°E	477m	1984-1987	13.5°	Elevated desert observatory; photoelectric + naked eye
Helwan	29.86°N, 31.34°E	114m	1984-1987	13.1°	Peri-urban; slight light pollution
Aswan	24.09°N, 32.90°E	92m	1984-1987	14.0°	Near-equatorial desert; clearest conditions
Siwa Oasis	29.20°N, 25.52°E	-18m	2005-2007	14.8°	Below sea level; very dry; exceptional clarity
Mersa Matrouh	31.36°N, 27.24°E	26m	2005-2007	13.7°	Mediterranean coast
Assiut	27.17°N, 31.17°E	55m	2010-2013	13.7°	Nile Valley; agricultural; slightly lower than desert

Second NRIAG Paper

Hassan, A.H., et al. "Determination of Fajr twilight at five Egyptian sites." NRIAG Journal of Astronomy and Geophysics, 5: 9-15, 2016.

Sites: Sinai (31.07°N, 30m), Assiut (27.17°N, 55m), Kharga Oasis (25.45°N, 74m), Qena (26.16°N, 96m), and others. Results consistent with earlier campaign: 13°-15°.

Sinai desert specifically: 14.84° mean angle (n=47 nights). Nile Valley sites: systematically lower by ~1° (agricultural aerosols reducing sky clarity).

Isha Findings

The same papers cover Isha (Shafaq al-Abyad, white dusk twilight):

Mean Isha angles: 14.3°-15.8° across Egyptian sites
Shafaq al-Ahmar (red dusk) disappears earlier: ~10°-12°

Key Conclusions

The 18° convention overstates true dawn by a significant margin. At most Egyptian sites, the sky begins to lighten at 13°-15° depression.
Desert sites consistently yield slightly higher angles than agricultural or coastal sites, likely due to atmospheric aerosol differences.
Results are consistent across a 30-year span (1984-2014) and multiple independent teams.
No systematic seasonal trend is reported — but Egypt spans only 22°-31°N, limiting latitude range for seasonal analysis.

Data Note

These papers report mean angles and statistical distributions, not per-date timestamps with explicit times. The per-date ML training records for Egypt in this project are derived from the published means using estimated observation times, and are marked accordingly in data/raw/sources.md.

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