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pray-calc-ml/research/aggregate_comparison.md
Aric Camarata c1eeef53c4 Expand dataset to 5,871 Fajr / 46 Isha across 114 locations 
Major additions:
- Extract all 1,621 Basthoni 2022 SQM records (46 Indonesian sites,
  Lampiran 2-5) via precomputed_angles.py
- Add 9 new raw sighting CSVs: Abdel-Hadi Malaysia, BRIN multistation,
  Kassim Bahali (2017+2019), Khalifa Saudi, Moonsighting.com,
  Shaukat 2015 Blackburn UK, Walisongo Sulawesi
- Curate aggregate D0 database (115 entries) in research/

Pipeline improvements:
- Open-Topo-Data SRTM30m primary elevation API with fallback
- APPROVED_RAW_CSVS allowlist prevents circular data ingestion
- Pre-computed angle merge path (bypasses back-calculation for SQM data)
- BAD_NOTE_MARKERS quality filter for excluded sources

Collection tools:
- BRIN multistation SQM processors
- PDF/HTML table extractor for academic papers
- Source tracking database (collection_manifest.json)

Documentation:
- Rewrite .wiki/Data.md and .wiki/Research.md from scratch
- Expand Data-Sources.md with full Basthoni Lampiran breakdown
- Add 14 researcher outreach drafts
- Update .gitignore to exclude bulk/experimental files
2026-02-28 10:51:01 -05:00

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Aggregate D0 Values: Comparison Across Published Research

This file compiles all known aggregate solar depression angles (D0) for Fajr and Isha from published academic research. These are NOT per-night observation records. They represent mean angles reported across multi-night observation campaigns.

The structured data is in aggregate_d0_values.csv (same directory).

Key Findings

Fajr Depression Angle by Sky Quality

Sky Quality D0 Range Mean D0 Method Notes
Pristine/dark 15.5-19.9 17.5 SQM, naked-eye Banyuwangi 19.9, Labuan Bajo 19.3, Jordan 19.5, Karimunjawa 15.5, Agam 16.7
Rural/somewhat dark 13.4-17.6 15.0 SQM, DSLR, photometer LAPAN stations, Tilong 14.4, Malaysian coast, Egyptian desert, Biak 13.4
Suburban/somewhat bright 12.3-17.0 13.8 SQM Bosscha 13.7, Pasuruan 13.9, Pontianak 12.3, Subang 12.7
Urban/bright 9.1-14.0 12.6 SQM Mangkangkulon 12.8, Medan 11.9, Depok 13.6, 15th of May City 12.7

Isha Depression Angle by Sky Quality

Sky Quality D0 Range Mean D0 Method Notes
Pristine 17.5-18.9 17.7 SQM, naked-eye Coonabarabran, Sabah, Kelantan coast
Rural 14.0-16.5 15.4 SQM Malaysia east coast, Egypt
Urban (LP) 11.5-12.9 12.2 SQM Putrajaya, Kuala Lumpur

Regional Summary

Southeast Asia (Indonesia + Malaysia)

  • 58 Fajr entries, 16 Isha entries (including 15 Basthoni 2022 per-site means)
  • Latitude range: 10.1S to 7.2N (equatorial)
  • Fajr D0: 11.9-19.9 (wide range driven by light pollution gradient)
  • Dark Indonesian sites (Banyuwangi, Labuan Bajo, Mombhul Beach): 19.1-19.9
  • Basthoni 2022 dark-sky mean across 594 nights: 16.3
  • Basthoni 2022 somewhat dark mean across 380 nights: 14.1
  • Basthoni 2022 somewhat bright mean across 418 nights: 13.4
  • Basthoni 2022 bright/urban mean across 229 nights: 12.8
  • LAPAN 8-station mean: 16.51 (moderate sky quality)
  • Urban LP sites (Medan 11.9, Mangkangkulon 12.8, Depok 13.6): 11.9-13.6
  • Isha data mostly from Malaysian SQM campaigns: 11.5-18.0

Middle East / North Africa (Egypt, Saudi, Libya, Mauritania, Jordan)

  • 19 Fajr entries, 4 Isha entries
  • Latitude range: 18N to 32N
  • Fajr D0: 12.7-19.5 (Egypt urban vs Jordan pristine)
  • Egypt NRIAG multi-site mean: 14.56 (consistent across 6 sites)
  • Saudi Hail desert: 14.0 (SQM+photoelectric, 32 nights)
  • Libya Tubruq: 13.48 (1053 naked-eye observations)
  • Jordan pristine: 19.5 (naked-eye, very dark sites)

Europe / UK

  • 4 Fajr entries, 2 Isha entries
  • Latitude: 51.2N to 53.7N
  • Fajr D0: 15.0-18.0 (Blackburn to Ankara)
  • Isha D0: 15.0 (Exmoor, Blackburn)

Interpretation Notes

  1. Sky quality is the dominant factor in D0 variation. Pristine sites consistently produce 17-19 degree angles, while urban sites produce 12-14 degrees. This is not measurement error but reflects when the twilight signal becomes distinguishable from artificial sky glow.

  2. The Egypt NRIAG studies show remarkable consistency (14.5-14.7) across desert and Mediterranean sites, suggesting this is a robust estimate for low-LP Middle Eastern sites.

  3. The LAPAN 16.51 degree mean across 8 Indonesian stations is a good representative value for the region's typical sky quality.

  4. The 100k-row target in the PRI is aspirational. Published per-night observation data worldwide totals approximately 4,500-5,000 records (dominated by OpenFajr Birmingham). Reaching 10,000+ requires institutional data sharing.

Sources

See aggregate_d0_values.csv for the full structured dataset with coordinates, methods, and citations.