Naked eye observations for morning twilight at different sites in Egypt
Hassan, A., Abdel-Hadi, Y., Issa, I., Hassanin, N. (2014). Naked eye observations for morning twilight at different sites in Egypt. EKB Journal Management System, 3(1), 23-26. doi: 10.1016/j.nrjag.2014.02.002
A.H. Hassan; Yasser A. Abdel-Hadi; I.A. Issa; N.Y. Hassanin. "Naked eye observations for morning twilight at different sites in Egypt". EKB Journal Management System, 3, 1, 2014, 23-26. doi: 10.1016/j.nrjag.2014.02.002
Hassan, A., Abdel-Hadi, Y., Issa, I., Hassanin, N. (2014). 'Naked eye observations for morning twilight at different sites in Egypt', EKB Journal Management System, 3(1), pp. 23-26. doi: 10.1016/j.nrjag.2014.02.002
Hassan, A., Abdel-Hadi, Y., Issa, I., Hassanin, N. Naked eye observations for morning twilight at different sites in Egypt. EKB Journal Management System, 2014; 3(1): 23-26. doi: 10.1016/j.nrjag.2014.02.002

Naked eye observations for morning twilight at different sites in Egypt

NRIAG Journal of Astronomy and Geophysics
Volume 3, Issue 1, June 2014, Pages 23-26    PDF (364.82 K)
DOI: 10.1016/j.nrjag.2014.02.002
Authors
A.H. Hassan; Yasser A. Abdel-Hadi; I.A. Issa; N.Y. Hassanin
Abstract
Twilight observations were carried out in the period between 1984 and 1987 in different seasons at different sites of Egypt (Baharia, Matrouh, Kottamia and Aswan) through a cooperation project between Dar El-Iftaa’ and the Egyptian Academy of Scientific Research and Technology. Naked eye observations of the first light of the dawn were done in parallel to the photoelectric measurements of the twilight phenomena. The depression of the sun below the horizon corresponding to the first light was calculated from the time of observations. Our estimates show that the normal eye can just discriminate the dawn (the first white light thread) at a depression of 14.7° with a maximum value of 15.08° and a minimum value of 12.01°. This result agrees with result obtained by our previous photoelectric measurements.
Keywords
Naked eye; Twilight observations; Bahria; Matrouh; Kottamia; Aswan
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