André Danjon
André-Louis Danjon (born April 6, 1890 in Caen , France , † April 21, 1967 in Suresnes , Hauts-de-Seine ) was a French astronomer .
Danjon developed a method for measuring the Erdscheins , the opposing note the earth on the moon . He used a telescope with a prism that split the light of the moon into two identical bundles of light, so that two identical images of the moon were created side by side. With a shutter, one of the images was darkened to such an extent that its sunlit moon side had the same brightness as the moon side in the non-dimmed image, which was only illuminated by earth light.
With the dimming required for this, Danjon received a quantitative measurement value for the brightness of the earth as seen from the moon. Danjon also examined the brightness of the light deflected by the earth's atmosphere in the umbra of the earth during total lunar eclipses (which varies depending on atmospheric pollution) . He summarized these in the Danjon scale named after him , which ranges from 0 (very dark) to 4 (very light).
The Geodetic Astronomy owes him Danjon-astrolabe ( "L'Astrolabe impersonnel de L'Observatoire de Paris", published 1955), a further development of Prismenastrolabiums of Claude and Driencourt for astronomical latitude and longitude determination by the method of equal heights . What is essential is an improved beam path and a registration micrometer with which the personal equation (time delay) of the observer is eliminated.
Furthermore, Danjon postulated the so-called Danjon limit from his own observations, the observations of others and mathematical considerations . It says that the crescent moon can no longer be observed from a distance of less than seven degrees from the sun .
1930–1945 Danjon headed the Strasbourg observatory , 1945–1963 the Observatoire de Paris .
Awards and memberships
- 1948 member of the Académie des Sciences
- 1950 Jules Janssen Prize
- 1958 Gold Medal from the Royal Astronomical Society
The asteroid (1594) Danjon bears his name in his honor, as does the moon crater Danjon .
Web links
- Publications by A. Danjon in the Astrophysics Data System
- Obituaries for A. Danjon in the Astrophysics Data System
Individual evidence
- ↑ Information on André Danjon in the database of the Bibliothèque nationale de France , accessed on October 4, 2019.
| personal data | |
|---|---|
| SURNAME | Danjon, André |
| ALTERNATIVE NAMES | Danjon, André-Louis (full name) |
| BRIEF DESCRIPTION | French astronomer |
| DATE OF BIRTH | April 6, 1890 |
| PLACE OF BIRTH | Caen , France |
| DATE OF DEATH | April 21, 1967 |
| Place of death | Suresnes , Hauts-de-Seine |