Johann Gottlieb Friedrich Schrader
Johann Gottlieb Friedrich Schrader (born September 17, 1763 in Salzdahlum near Wolfenbüttel , † probably 1833 ) was a German physicist and chemist . Together with the astronomer Johann Hieronymus Schroeter , he developed processes for optimizing metallic telescope mirrors.
Schrader had studied chemistry and physics at the universities of Kiel and Göttingen .
In 1790 he accepted an unpaid teaching position in Kiel. He was later appointed professor there. He became known through physical experiments that he financed himself.
Schrader was interested in astronomy and constructed mirror telescopes based on the model of the devices of Wilhelm Herschel, who lived in England .
In April 1792, he sought to Johann Hieronymus Schroeter, who in Lilienthal in Bremen , the observatory Lilienthal had founded. By January 1793, both carried out experiments to optimize telescope mirrors, which at the time were not made of glass , but metal . The two developed a whitish, brittle alloy of copper and tin to which they added arsenic . To increase the reflectivity , they evaporated an additional layer of arsenic. Telescopes with very good imaging performance were created.
Schroeter, who previously its levels of William Herschel from England had taken was to create from now on be able to own mirror, he assisted his gardener Harm Gefken. In 1794 the then famous “Lilienthal Giant Telescope” with a 50 cm opening was completed.
Schrader went back to Kiel and also made telescope mirrors. In April 1793 he manufactured a complete telescope with a 2.1 m focal length for Wilhelm Knebel, envoy of the Kingdom of Hanover at the court of Württemberg . It later came into the possession of Johann Wolfgang von Goethe , who used it to make observations of the earth's moon . Goethe wanted to sell the device again but couldn't find a buyer because of the high price. In 1813 he bequeathed it to the newly founded observatory of the University of Jena . It is still owned by the university today.
literature
- Karl Ernst Hermann Krause: Schrader, Johann Gottlieb Friedrich . In: Allgemeine Deutsche Biographie (ADB). Volume 34, Duncker & Humblot, Leipzig 1892, p. 740.
- Felix Lühning: Schrader, Johann Gottlieb Friedrich. In: New German Biography (NDB). Volume 23, Duncker & Humblot, Berlin 2007, ISBN 978-3-428-11204-3 , p. 510 ( digitized version ).
Web links
| personal data | |
|---|---|
| SURNAME | Schrader, Johann Gottlieb Friedrich |
| BRIEF DESCRIPTION | German physicist and chemist |
| DATE OF BIRTH | 17th September 1763 |
| PLACE OF BIRTH | Salt dahlum |
| DATE OF DEATH | uncertain: 1833 |