Ertel & Sohn (fl. 1821- 1984), München.

Traugott Leberecht von Ertel (*1778;†1858) [5]
Traugott Leberecht von Ertel (*1778;†1858) [5]
The T. Ertel & Sohn Reichenbach'sche Mathematisch-mechanisches Institut, Louisenstraße 5, München. The factory was renamed Ertel-Werke in 1921. The building was destroyed during the war in 1944. [5]
The T. Ertel & Sohn Reichenbach'sche Mathematisch-mechanisches Institut, Louisenstraße 5, München. The factory was renamed Ertel-Werke in 1921. The building was destroyed during the war in 1944. [5]

Ertel catalogue undated, c. 1920s. Cataloghi di strumenti scientifici nella biblioteca dell'Osservatorio Astronomico di Palermo.

ERTEL

Traugott Leberecht von Ertel (1778-1858). 1806, worked for Reichenbach, Utzschneider, und Liebherr (est. 1804, geodetic instruments). 1814, left that business with Reichenbach. 1821, became owner of 'T. Ertel & Sohn, Reichenbach'sches Mathematisch Mechanisches Institut' (name in 1834, when catalog listed 69 items). 1858, 100 employees. 1850 address, Karls Strasse, Munich; near to G & S Merz, also established by Reichenbach. Sons: Georg Ertel (1813-1863); Gustav Ertel (1829-1875), joined business. Gustav later owner, his son Georg an employee but left in 1876. Moritz Roehrer technical director, 1876 resigned & replaced by August Dietz (1848-1920), employee since 1866. Meridian circle for Vanderbildt Univ., Tennessee, 1878. Transit instrument at Bucknell University, Pennsylvania. 1890, Diez purchased Ertel, used name T. Ertel & Sohn. 1911, Julius Rinnebach joined firm, incorporated as 'T. Ertel & Sohn G.m.b.H., mathematisch-mechanisches Institut fuer geodaetische und militaerwissenschaftliche Instruments'. Technical director Adolf Hahn. Other managers, Walter Preyss (1879-1942), son Carl Preyss (director in 1945, 1981 still owner & manager). 1983, Ertel operating in Puchheim, suburb of Munich, 150 employees, specializing in theodolites, no astronomical instruments, 'Ertel-Werk fuer Feinmechanik'. Ertel goes bankrupt in 1984. 

Ertel & Sohn Kilometerzirkel

Kilometer compass invented by Ludwig Sailer, and made by Ertel & Sohn. The signature is Sailer Prlt; a Google search reveals that Prlt stands for Premier Lieutenant, first lieutenant in English. The compass comes in a leather sheath and measures 130mm in length. An exact date is difficult to determine, but probably 1870-1890.

See also Himmel's Kilometerzirkel.

Ertel & Sohn double optical square ca. 1875. 

See Bauernfeind double optical square.

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NOTES / REFERENCES

[1] Ertel Biography https://de.wikisource.org/wiki/ADB:Ertel,_Traugott_Leberecht_von

[2] Baur, Franz; Lehrbuch der niederen Geodäsie, Wilhelm Braumüller, Wien 1871. page 79.

[3] Heer, Rainer; Biographien von Herstellern zur geodätischen Messtechnik in der geodätischen Sammlung des Geodätischen Instituts der Leibniz Universität Hannover

[4] Ertel catalogue http://www.astropa.unipa.it/biblioteca/Strumenti/e-catalogues/Ertel-Werke/Catalogo.html 

[5] Preyss, C.R.;  Von Reichenbachs Werkstatt zum Ertel-Werk für Feinmechanik 1802-1962, München 1962.

[6] Plan of Munich 1806 (centre only) with house numbers.

[7] Plan of Munich with Ertels location in 1830, before the house renumbering.

[8] Plan of Munich with Ertel's location in 1833 after the house renumbering.

[8] Plan of Munich 1910 with house numbers (at the street corners).

[9] Artistisches München im Jahre 1835, oder Verzeichniss gegenwärtig in Bayerns Hauptstadt...1835 p. 27 Google Books.

[10] LUDWIG SAILER

[11] Königlich bayerische Haupt und Residenzstadt München nach der neuen Hausnummerirung 1833. p.158. Google Books

[12] Dyck, Walther von; Georg von Reichenbach, Selbstverlag des Deutschen Museums, München 1912. Internet Archive 

[13] Ertel-Werk Wikipedia  

[14] Lagemann, Robert. The Garland Collection of Classical Physics Apparatus at Vanderbilt University. Nashville: Folio, 1983. 317pp.

[15] Vogler, Christian August; Abbildungen geodätischer Instrumente 36 Lichtdrucktafeln nebst Text, 1892. Deutsches Museum.