# Research Archive

This folder contains summaries of academic and institutional research on Islamic twilight
angles. These papers describe other researchers' conclusions about the solar depression angle
at Fajr and Isha. They are useful for understanding the scientific landscape but are **not**
used as ML training data — only raw per-date observations with explicit timestamps feed
the `data/processed/` datasets.

## Summary: What the research says

Most peer-reviewed naked-eye studies find Fajr (true dawn / Subh Sadiq) corresponds to a
solar depression of roughly **13°–16°** depending on site, season, and atmospheric conditions.
Isha (Shafaq al-Abyad, white dusk twilight) corresponds to roughly **14°–18°**.

The classic convention of 18° Fajr (used by ISNA, MWL, and others) is based on astronomical
twilight (the sky becoming fully dark), not the first appearance of dawn light. Observations
consistently show true dawn appears while the sun is 12°–15° below the horizon, not 18°.

## Papers Summarized

| File | Authors | Year | Site | Finding |
| --- | --- | --- | --- | --- |
| `nriag-egypt-1984-2014.md` | Hassan et al. | 1984-2014 | Egypt (6 sites) | 13°-15° Fajr |
| `nriag-egypt-2022-2025.md` | Rashed et al. | 2018-2025 | Egypt (Fayum, Alex) | 13°-14° Fajr |
| `hail-saudi-2018.md` | Khalifa | 2014-2015 | Hail, Saudi Arabia | 14° mean Fajr |
| `malaysia-indonesia-2018.md` | Kassim Bahali | 2017 | KL + Indonesia | 16.67° Fajr |
| `depok-indonesia-2020.md` | Saksono | 2015 | Depok, Java | ~16° Fajr |
| `uk-observations.md` | Yusuf, Hizbul Ulama | 1987-2017 | UK (3 sites) | 12°-14° Fajr |
| `birmingham-openfajr.md` | OpenFajr project | 2016-2026 | Birmingham | 12.5°-14° Fajr |
| `moonsighting-global.md` | Khalid Shaukat | 2000s | Multiple global | 15°-18° Fajr |