(in visual photometry)
31Luminous efficacy — is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source s output, or it can be the total electric power consumed by… …
32Candela per square metre — Nit (unit) redirects here. For the unit of information entropy, see Nat (information). The candela per square metre (cd/m2) is the derived SI unit of luminance. The unit is based on the candela, the SI unit of luminous intensity, and the square… …
33Observational astronomy — Mayall telescope at Kitt Peak National Observatory Observational astronomy is a division of the astronomical science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the… …
34Proxima Centauri — Coordinates: 14h 29m …
35National Australian Convention of Amateur Astronomers — The National Australian Convention of Amateur Astronomers (NACAA) is a biennial national forum for amateur astronomy in Australia. In 1966 two enthusiastic amateur astronomical groups, the James Cook Astronomers Club and the Canberra Astronomical …
36Cosmic infrared background — (CIB) is a mysterious infrared light coming from outer space. It is slowly being resolved into specific sources by infrared telescopes. In some ways it is analogous to the cosmic microwave background, but at shorter wavelengths. Contents 1… …
37Alpha Centauri — This article is about α Centauri . For a Centauri , see V761 Centauri. For A Centauri , see A Centauri. For other uses, see Alpha Centauri (disambiguation). Alpha Centauri A[1]/B[2] …
38Star catalogue — An illustration of the Perseus constellation (after Perseus from Greek mythology) from the star catalogue published by the German astronomer Johannes Hevelius in 1690 A star catalogue, or star catalog, is an astronomical catalogue that lists… …
39Próxima Centauri — Coordenadas: 14h 29m 42.9487s, −62° 40′ 46.141″ Próxima Centauri …
40Optics — For the book by Sir Isaac Newton, see Opticks. Optical redirects here. For the musical artist, see Optical (artist). Optics includes study of dispersion of light. Optics is the branch of …
