Improving the crescent visibility limits due to factors causing decrease in the sky twilight brightness |
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| Authors: | J S Mikhail A S Asaad S Nawar N Y Hassanin |
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| Institution: | (1) National Research Institute of Astronomy and Geophysics Helwan, Cairo, Egypt |
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| Abstract: | The measured sky twilight brightness of a site is believed to be connected with main factors such as geographical latitude, elevation of the site above sea level, the season of observations and the aerosol pollution. These factors may decrease the sky twilight brightness and thus improve the crescent visibility limits. The effect of these factors on the visibility conditions to see the new Moon are investigated in the present work. The results show that the visibility conditions has improved at sites situated at higher northern geographical latitudes and higher elevation above sea level. The conditions to see the new Moon in winter season is better than the summer season. The aerosol pollution has a great effect on the visibility of the new Moon at sun's depression 5°, while for sun's depression greater than 5° the aerosol pollution has a small effect. |
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