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atomqwerty
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Homework Statement
Evening civil twilight (civil dusk) begins at sunset and ends when the geometric center of the sun reaches 6° below the horizon. Calculate for an observer at latitude = 45º the duration of his civil dusk in march 21st (when [tex]\delta_{sun}=0º[/tex]
Homework Equations
The equations of the transformation between horizontal coordinates and ecuatorial coordinates
"http://en.wikipedia.org/wiki/Celestial_coordinate_system#Equatorial_to_horizontal_coordinates"
The Attempt at a Solution
Let us do a = 0 (sun over the horizon). This implies cos h = -tan d tan f (h: hour angle, d: declination, f: latitude). If d = 0 (delination of the sun is zero on march 21st), then we have h = 90º. Thus A = 90º too (azimut). Is this correct?
doing the same for a =-6º I obtain that the difference between hour angles for the two positions (sun in a=0 and sun in a=-6) is 8.51º. How can I transform this into minutes?
Thanks