Description

Description: A significant letter between two prominent astronomers! In this autograph letter signed, Bessel informs Herschel about the published “List of Declinations” which he has sent to the Astronomical Society. He hopes that his new device will establish a general agreement, which is still wanting, in the definition of declinations [one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system]. The “158 Sweeps”–that he began in August 1821 without interruptions–he says are in accordance with the Society’s intentions. He also takes the liberty of sending copies of his Observations to Herschel with a request to forward them to the Royal Society, the Astronomical Society, Edinborough Society and Mr. Pond. The letter is in German and includes a full English transcript.

Written on a 10” x 8” sheet of  ivory paper from Koenigsberg and dated 11 April 1823. Item #A01836

Friedrich Wilhelm W. Bessel (1784-1846) was a German astronomer, mathematician, physicist, and geodesist. He was appointed the Director of the Konigsberg observatory founded by Frederich Willheim III of Prussia and Professor of Astronomy at the Albertus University (1809). He was the first to make reliable calculations measuring the distance to a fixed star and the first to measure and publish a parallax. His contribution to geophysics was the determination of the lengths of the simple seconds’ and seconds’ pendulum. His investigations eventually led to an international standardization of weight and measures.

Sir John F. W. Herschel 1st Baronet (1792-1871) was a mathematician, inventor, astronomer and an accomplished chemist. As an astronomer, he studied binary stars to arrive at an understanding of gravitational forces, invented a way to measure solar radiation, recorded the locations of as many as 68, 948 stars, observed Halley’s comet, and the satellites of Saturn. He wrote Outlines of Astronomy (1849), a book for educated lay people. He is as important as William Henry Fox Talbot and Louis-Jacque-Mande Daugerre in photographic circles for his discovery of “hypo” (hyposulphite) as a fixing agent in photography. He also coined the terms, snapshot, positive and negative and possibly “photography” as well. He was a life-long mentor to the photographer Julia Margaret Cameron.

Condition: Left blank margin has mounting glue residue, mailing fold lines. Generally very good condition.