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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
39 lines
1.6 KiB
Markdown
39 lines
1.6 KiB
Markdown
# Hail, Saudi Arabia — Khalifa 2018
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## Paper
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Khalifa, A.S. "Astronomical determination of Fajr and Isha prayer times at Hail, Saudi Arabia."
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*NRIAG Journal of Astronomy and Geophysics*, 7: 22-28, 2018.
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## Location
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Hail (27.52°N, 41.70°E, ~1020m elevation) — a city on the Najd plateau in central Saudi Arabia.
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The high elevation and desert conditions produce excellent sky transparency.
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## Method
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80 total observation nights in 2014-2015. 32 nights selected for excellent atmospheric
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visibility (no clouds, no dust). Naked-eye observation by trained observers.
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## Results
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- **Mean Fajr depression:** 14.4° (range 12.8°-16.1°)
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- **Mean Isha depression (Shafaq Abyad):** 14.8° (range 13.2°-16.4°)
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- **Seasonal variation:** Higher angles in winter, lower in summer (consistent with other studies)
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## Significance
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At 1020m elevation, Hail is the highest-elevation site in the Saudi/Gulf region with published
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Fajr observations. The results show a slightly higher mean angle than sea-level desert sites
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in Egypt (13.5°-14.5°), consistent with the hypothesis that elevation increases the apparent
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depression angle at true dawn (the observer is above more of the atmosphere, so the first light
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of dawn appears at a slightly steeper angle).
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The Hail dataset is particularly useful for the elevation variable in the ML model — it is one
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of the few high-altitude desert sites with per-season data.
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## Note for ML Training
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The per-season records in `verified_sightings.py` for Hail are constructed from the paper's
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reported seasonal means, with observation times estimated from sunrise data. They are marked
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as "time inferred" in `data/raw/sources.md`.
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