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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
75 lines
3 KiB
Markdown
75 lines
3 KiB
Markdown
# Malaysia and Indonesia Studies
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## Kassim Bahali et al. 2018 (DSLR Study)
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**Paper:** Kassim Bahali, N.F., et al. "Determination of Fajr and Isha prayer times based on
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astronomical observation at low latitude." *Sains Malaysia*, 47(11): 2797-2805, 2018.
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**Location:** Kuala Lumpur and surrounding Malaysia/Indonesia sites (2°N-7°S range)
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**Method:** DSLR astrophotography + SQM (Sky Quality Meter) sky brightness
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**Data:** 64 observation days, February-December 2017
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**Key result:** Mean Fajr depression = **16.67°** (range 13.9°-19.8°)
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The DSLR + SQM combination is methodologically stronger than naked-eye only. The SQM
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provides an objective measure of sky brightness that eliminates observer subjectivity.
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At near-equatorial latitudes (2°-7°), the Sun rises and sets at a steep angle through the
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horizon, producing very short, sharp twilight transitions.
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---
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## Saksono 2020 (Depok, Indonesia)
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**Paper:** Saksono, T. "Fajr prayer time determination using the Sky Quality Meter."
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*NRIAG Journal of Astronomy and Geophysics*, 9(1): 238-244, 2020.
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**Location:** Depok, West Java, Indonesia (6.4°S, 106.83°E, 65m)
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**Method:** SQM sky brightness monitoring; 26 nights June-July 2015
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**Result:** ~16° mean Fajr depression
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---
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## Hamidi 2007-2008 (Malaysia Isha Study)
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**Source:** Zety Sharizat Hamidi, *Determination of Isha prayer time based on shafaq abyad in
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Malaysia.* Academia.edu, 2008.
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**Location:** Two sites:
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- Kuala Lipis: 4.183°N, 102.040°E, 76m (east coast)
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- Port Klang: 3.004°N, 101.403°E, 5m (west coast)
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**Method:** Naked-eye observation of Shafaq al-Abyad disappearance; May 2007 - April 2008
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**Result:** Isha (Shafaq Abyad) consistently at approximately **16°-17°** depression
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---
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## OIF UMSU (Medan, North Sumatra 2017-2020)
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**Location:** OIF (Observatory of Islamic Fajr) at University of Muhammadiyah North Sumatra,
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Medan (3.595°N, 98.672°E, 22m)
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**Method:** SQM photometry; hundreds of observation days
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**Proposed angle:** 16.48° for Indonesian national standard
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---
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## Key Pattern: Equatorial Sites Yield Higher Angles
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All Malaysia/Indonesia studies find Fajr at ~16°-17°, compared to ~13°-14° in Birmingham
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and the UK. This is a systematic and significant pattern:
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| Latitude | Representative Site | Mean Fajr Angle |
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| --- | --- | --- |
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| 52°N | Birmingham, UK | ~13° |
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| 40°N | Ankara, Turkey | ~15° |
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| 30°N | Egypt (desert) | ~13.5°-14.5° |
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| 27°N | Hail, Saudi Arabia (1020m) | ~14.4° |
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| 3°-7°N | Malaysia/Indonesia | ~16°-17° |
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| 3°-7°S | Indonesia (Java) | ~16°-17° |
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| 33°-37°S | Cape Town / Auckland | ~15°-16° |
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This counter-intuitive result (equatorial sites have *higher* angles than mid-latitude sites)
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is likely caused by the geometry of the Earth's atmosphere: at equatorial latitudes, the Sun
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rises at a steeper angle through the horizon, so morning twilight is briefer and more intense.
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The same absolute angle corresponds to a later moment relative to sunrise at lower latitudes.
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The ML model should capture this latitude-dependent pattern.
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