Pixel (astronomical navigation)

In astronomical navigation, the point at which an imaginary line from the center of an observed astronomical celestial body to the center of the earth intersects the surface of the earth is referred to as the image point of a star (English: spot, substellar point) . For an observer standing in the celestial image point on the earth's surface, the celestial body is at the zenith at the time of observation .

The pixel is of great importance in astronomical navigation. In the nautical yearbook , the geographic coordinates of the pixels of many celestial bodies are recorded for every hour on the hour and can be determined for every second by interpolation. With the help of a precise time determination ( chronometer ) and an altitude angle measurement with the sextant , a base line for your own location can be obtained from the pixel coordinates and the altitude angle measured . This stand line is a circle on the surface of the earth, the center of which is the image point of the star; the radius can in practical cases be a few hundred kilometers. If you have a rough knowledge of the location, it is sufficient to look at the relevant small segment of a circle near the location - or the tangent.

literature

• Walter Stein: Astronomical Navigation. Verlag Klasing & Co. GmbH, Bielefeld 3rd edition, 1974 - p. 118 and the following KYB, volume 21; ISBN 3-87412-019-8 ; New edition from 1989 under ISBN 3-87412-095-3 .
• Mary Blewitt: Practical Navigating for Stars . Verlag Klasing & Co. GmbH, Bielefeld, 1975 - p. 14 and following, KYB Volume 34; Original edition: Celestial Navigation for Yachtsmen. Stanford Maritime Ltd. 12 Long Acre London WC2E 9LP, 6th Ed., M. Blewitt 1971/75.