| Benjamin Peirce - Plane trigonometry - 1845 - 498 pages
...times of their rising and setting ; and the star will not set until its zenith distance is 90° -j- horizontal refraction, and the corresponding hour...horizon, when the height of the eye is twenty feet. Dip. 2. Find the dip of the sea at the distance of 3 miles, when the height of the eye is thirty feet.... | |
| Joseph Anthony Gillet, William James Rolfe - Physics - 1881 - 544 pages
...shine on the lower layers at night, or before it has begun to shine upon them in the morning. Twilight begins and ends when the sun is about 18° below the horizon. 592. Color of the Sky. — Large particles reflect and diffuse all luminous waves equally well, but... | |
| Joseph Anthony Gillet, William James Rolfe - Physics - 1881 - 342 pages
...shine on the lower layers at night, or before it has begun to shine upon them in the morning. Twilight begins and ends when the sun is about 18° below the horizon. 451. Color of the Sky. — Large particles reflect and diffuse all luminous waves equally well, but... | |
| John Bradley Harbord - Naval art and science - 1883 - 472 pages
...doubtful " light which precedes the rising of the sun and follows its setting, called twilight. Twilight begins and ends when the sun is about 18° below the horizon ; and its duration, therefore varies with the latitude, for the time which is required for the sun... | |
| John Ellard Gore - Astronomy - 1893 - 152 pages
...sun." Twilight. The refracted sunlight visible after the sun has set, or before it rises. Twilight begins and ends when the sun is about 18° below the horizon. On the "longest day" the sun is about 23 g° north of the celestial equator. Its zenith distance is... | |
| Naval art and science - 1894 - 1230 pages
...doubtful light which precedes the rising of the sun and follows its setting, called twilight. Twilight begins and ends when the sun is about 18° below the horizon, and its duration therefore varies with the latitude." To find the time, therefore, that twilight will... | |
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