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
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UK Fajr and Isha Observations
Hizbul Ulama UK — Blackburn (1987-1989)
Location: Rural outskirts of Blackburn, Lancashire (53.748°N, 2.48°W, ~120m) Source: http://www.hizbululama.org.uk/files/salat_timing.html
A systematic observation program conducted over two years with 21 successful Fajr sightings and corresponding Isha (Shafaq al-Abyad) records. Observations were made from a dark rural site in northwest England.
At 53.7°N, this is among the highest-latitude systematic Fajr studies on record. Key findings:
- Summer solstice observations are particularly important — at 54°N in June, true dawn appears at a very early local time and the sun's arc through the horizon zone is extremely shallow
- Winter Fajr requires very long darkness periods to observe
- Shafaq al-Abyad (Isha) does not fully disappear in summer at this latitude — a controversial finding with significant fiqh implications
The 21 observations are spread across all seasons. Times are published to the nearest minute in the Hizbul Ulama account.
Asim Yusuf — "Shedding Light on the Dawn" (2013-2016)
Location: Exmoor National Park (51.15°N, 3.65°W, ~430m); Exmoor is an International Dark Sky Reserve — one of the darkest locations in southern England. Source: ISBN 978-0-9934979-1-9 (2017)
This is the most scholarly treatment of the UK Fajr controversy. Asim Yusuf conducted 18 multi-observer sighting sessions at three dark-sky UK sites between 2013 and 2016, covering all four seasons at each site. His methodology:
- Multiple independent observers present simultaneously
- Detailed photographic documentation
- Explicit recording of "awwal al-tulu'" (first detectable light) vs "Fajr Sadiq" (true dawn)
- Elevation correction (Exmoor at 430m is significantly above the surrounding valley)
Key results: Consistent findings of true dawn at 12°-14° depression at Exmoor. The summer solstice observation is critical — at 51°N in June, the sun barely reaches 15° below the horizon, making the summer Fajr time very late (after midnight local time).
The Exmoor site at 430m is relevant to the elevation variable: being significantly elevated above the surrounding valley and atmosphere extends the observability of twilight phenomena.
Isha findings: Shafaq al-Abyad (white twilight) disappearance observed at 15°-17° depression in winter and autumn, with later times in summer (longer twilight persistence at 51°N).
Fiqh Implications
Both the Blackburn and Exmoor studies raise challenging questions for high-latitude UK communities:
- The 18° convention places Fajr unrealistically early in summer (before astronomical midnight)
- The observed 12°-14° is more consistent with what the human eye actually perceives as dawn
- Yusuf's work contributed to the ongoing academic discussion about whether high-latitude communities should use a different calculation method
Impact on pray-calc
These UK observations at 51°N-54°N are critical anchor points for the latitude variable in the ML model. They demonstrate that depression angle varies with latitude (52°N Birmingham at ~13°, versus tropical sites at ~16°-18°) and suggest a latitude-dependent correction term may be needed in any generalized algorithm.