François Arago, Astronomie Populaire, First Edition

M. J-A Barral, Astronomie Populaire par François Arago, 1856 - 1858, Paris, Gide et Baudry, Editeurs, 4 volumes, first edition

Volume 1: 1854, 599 pages
Volume 2: 1855, 554 pages
Volume 3: 1856, 635 pages
Volume 4: 1857, 854 pages

François Arago (1786 - 1853) was one of the most influential persons in the early history of photography. Arago was also an important astronomer and director of the Paris Observatory.

Arago was the link between photography and astronomy.

The four books are an important landmark in the history of astronomy.

The engravings are of an exceptional beauty. The complete set of Astronomy Populaire is very rare. The two volumes edition is more common but the four volume edition with all the engravings is extremely rare.

Arago was concerned with optical instruments that proved useful for a variety of purposes, in physics and meteorology as well as in astronomy, for which they were mainly devised.

In 1811, he invented the polariscope to determine the degree of polarization of light rays by passing them successively through a mica or rock-crystal polarizer and an Iceland spar analyzer... He transformed it into a polarimeter which he used to verify one of the few mathematically expressed laws he discovered...

In 1815, he built a primitive cyanometer to measure the degree of blueness of the atmosphere. In 1833, he proposed a photometer to measure comparative intensities of stellar light.

He also perfected an ocular micrometer for measuring small angles, which was erroneously attributed to William Pearson. The workings of all these instruments, based upon polarization phenomena, were expounded with great clarity and enthusiasm in Arago's public lectures at the observatory, published posthumously as Astronomie populaire

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