# Naked Eye Observations for Morning Twilight at Different Sites in Egypt

**Authors:** A.H. Hassan, N.Y. Hassanin, Y.A. Abdel-Hadi, and I.A. Issa
**Year:** 2014
**Journal:** NRIAG Journal of Astronomy and Geophysics, 3: 23-26
**DOI:** 10.1016/j.nrjag.2014.02.002
**URL:** https://www.tandfonline.com/doi/full/10.1016/j.nrjag.2014.02.002
**Sites studied:** 4 sites in Egypt: Bahria, Matrouh, Kottamia, Aswan
**Observation method:** Naked eye
**Date range:** Multiple years (appears to be part of the 2007-2013 NRIAG campaign)

## Sites (from Tubruq 2015 paper Table 2)

| Site | Lat | Lng | Elevation | Background | D0 range |
|------|-----|-----|-----------|------------|----------|
| Bahria | 28 42.9'N | 29 59.82'E | 150m | Desert | 12.6-15.0 |
| Matrouh | 31 0.2'N | 27 51'E | 75m | Sea-Desert | 12.3-14.5 |
| Kottamia | 29 55.9'N | 31 49.5'E | 470m | Desert | 14.46-14.86 |
| Aswan | 23 48.22'N | 32 29.5'E | 250m | Desert | 12.46-13.96 |

## Summary

Part of the extensive NRIAG naked-eye twilight observation campaign. Reports D0 ranges (not single mean values) for each of the four sites, suggesting per-observer or per-season variation was recorded. The mean D0 across all four locations is reported elsewhere (Tubruq 2015 paper, Fayum 2022 paper) as 14.7 degrees.

Kottamia (470m elevation, desert) shows the narrowest range (14.46-14.86), suggesting the most consistent conditions at this elevated desert observatory. Aswan (250m, southern Egypt near Tropic of Cancer) shows the widest range and lowest values (12.46-13.96).

## Data Availability

**COULD NOT ACCESS FULL TEXT.** Taylor & Francis returned 403. The data known is from cross-references in other papers (particularly the Tubruq 2015 paper's Table 2 and the Fayum 2022 paper's Table 1).

If the full text can be obtained, it may contain per-night observation tables that would be extremely valuable (4 sites, likely dozens of observations per site).

## For ML Training

Already partially covered in the aggregate D0 database. If per-night data can be extracted from the full text, this would add significant value for the Egypt latitude band (23-31 deg N).