History of Astronomy

The Detection of Interstellar Molecules

The first interstallar molecules were discovered in 1937-1938. Three diatomic molecules were detected: methylidine CH, its positve ion CH+ and cyanogen CN. In the 1960s radiospectroscopy made it possible to detect more complicated molecules in space. And it was still not believed that more complex moleculed could be found for the gas of the clouds, like the Orion nebular, were too diffuse to form. Then the ultraviolet light was thought to destroy the formed molecules. In 1963 OH, the hydroxyl radical was detected. Many more molecules had been detected, 130 in number, until 2002. 

Star Catalogues and Maps

The first star catalogue was published by Ptolemy in the second century. Later this star catalogue was known as the almagest. Ptolemey’s catalogue was used until the 17 th century. In the 17 th to the 18 th century astronomers prepared another catalogue under the direction of Wilhelm Friedrich Argelander (1799-1875). Argelander and his assistants measured the positions of 320.000 stars and measured their magnitudes. This catalogue, called the Bonner Durchmusterung, contains all stars brighter than magnitude 9.5 between the north pole and -2° at the southern hemisphere. His work was later used as a model for two other large catalogues covering the whole sky. The total number of stars in these catalogues covering the whole sky. In the zone catalogues the main goal was to give the position of the stars as exact as possible. This German Catalogue of the Astronomische Gesellschaft was begun in 1870 and was completed at the end of the century.

Greenwich Observatory

The Greenwich observatory was found in the 17 th century to measure the positions of the stars more precisely. New stars maps had to be draws to get exacter positions on sea. Too many ships got lost because of bad navigation. The observatory was found by Charles II. His first Astronomer Royal was John Flamsteed. The determination of the position on sea was the measuring of the moon distances. The moon moves at his apparent disc within an hour. That is half a degree. His positions has to be measured with an accuracy of a thirtieth part of its diameter.  300 years ago this accuraycy could not be achieved. 

Nevil Maskelyne was the first Astronomer Royal who published his obervations regularly and made them available to other astronomers. He increased the accuracy of the instruments by applying greatest care to instrumental adjustments and introduced technical improvements. For the telescopes he used achromatic lenses. 

In 1835 Airy was appointed. A new era of precision and technological advances began. Like his predecessors, he paid great attention to the determination of the postions of the Moon, planets and stars. Airy's reflex telescope paved the way of obtaining time with greater accuracy. To achieve that he used the  railway telegraph system. 

Airy Discs

The Astronomer Royal Airy  is also famous for the Airy discs.  The Airy discs are use to proof the quality of your telescope. This diffraction pattern is caracterized by the wavelength of light illuminating the circular aperture.  This application of that concept is used in cameras, microscopes and telescopes .  What you see through a telescope is a spot with rings. This diffraction pattern is used to know how sesitive a telescope or the eye is. 

Tobias Mayer  a German Cartographer And The Moon Distances 

In the year 1753/54 Tobias Mayer sent his tables of the Moon and the reductions to the Astronomer Royal, Nevile Maskelyne, of the Observatory in Greenwich. The accuracy of the moon’s positions he achieved was 1 degree. That value is equivalent to an accuracy at sea of 40 km in longitude at mid-latitudes of the northern hemisphere.