Arch of vision
The arc of vision ( Latin arcus visionis ) describes the minimum distance between the sun and another celestial body , which is necessary to observe heliacal and acronymic rising and setting.
By definition, it is the depth of the sun measured at right angles below the horizon at the moment in which the celestial body reaches the horizon . The visual arc shows different values for each celestial body and for different observation locations, as various factors such as the apparent brightness of the star, extinction and atmospheric conditions influence the visual arc. Thus, air pollution and light pollution in the territory of a metropolitan increase the resources to perform a celestial body arc of vision considerably.
A frequently used approximation formula for the visual arc is:
- 10.5 ° + 1.4 ° Apparent brightness (in size classes)
See also
literature
- Rolf Krauss: Sothis and moon dates: studies on the astronomical and technical chronology of ancient Egypt . Gerstenberg, Hildesheim 1985, ISBN 3-8067-8086-X , pp. 40-41.
- Carl Schoch: The "Arcus Visionis" of the planets in the Babylonian observations , in: Monthly Notices of the Royal Astronomical Society , Vol. 84, p.731, Oxford 1924, bibcode : 1924MNRAS..84..731S
Individual evidence
- ↑ Computation of Visibility Phenomena ( English ) alcyone software. Retrieved October 27, 2019.
- ^ Pier Paolo Ricci: Almanacco astronomico 2013. Astronomical almanac 2013. lulu.com, 2012, ISBN 978-1291211573 . ( limited preview in Google Book search)