CHAPTER TWO continued...
Flamsteed’s Atlas Coelestis
Celestial mapping took another major stride in the 18th century with the work of the first Astronomer Royal of England, John Flamsteed (1646–1719), who catalogued nearly 3000 stars with unprecedented precision from the newly founded Royal Observatory at Greenwich. Flamsteed’s star catalogue was published posthumously in 1725 in Volume 3 of his Historia Coelestis Britannica; the catalogue section itself was called Catalogus Britannicus. Four years later came Atlas Coelestis, a set of 25 elegantly engraved celestial charts based entirely on Flamsteed’s own observations. The far southern skies, below the horizon of Greenwich, are covered by one small chart based on the observations made by Halley at St Helena. This southern chart depicts the 12 constellations of Keyser and de Houtman plus Halley’s own invention, Robur Carolinum, now obsolete.
Flamsteed’s stars were divided into 55 constellations. Two Ptolemaic constellations, Ara and Corona Australis, were omitted because they were too far south for him to see. He accepted six of the constellations invented by Hevelius (Canes Venatici, Lacerta, Leo Minor, Lynx, Sextans, and Vulpecula), whereas today’s sky includes a seventh, Scutum; this was reinstated by Johann Bode in his Uranographia of 1801. Flamsteed’s remaining three non-Ptolemaic constellations were Camelopardalis, Coma Berenices, and Monoceros.
In the Atlas Coelestis, Flamsteed took particular care to depict the Greek constellation figures exactly as Ptolemy had described them. The introduction to the atlas contains some disapproving words about the way that Bayer had represented the constellation figures in his Uranometria:
‘Having drawn all his human figures, except Boötes, Andromeda and Virgo, with their backs towards us, those stars, which all before him place in the right shoulders, sides, hands, legs or feet, fall in the left, and the contrary ... whereby he renders the oldest observations false or nonsense.’
Despite popular misconception, Flamsteed did not introduce the so-called Flamsteed number system for identifying the stars in each constellation; that was done in 1783 by the French astronomer Joseph Jérôme de Lalande (1732–1807). In a French edition of Flamsteed’s catalogue Lalande inserted a column in which he numbered the stars consecutively in each constellation in the order that Flamsteed had listed them, and this is the system that astronomers mean when they speak of Flamsteed numbers. Stars are usually referred to by their Flamsteed numbers – for example 61 Cygni or 70 Ophiuchi – only when they are not already identified by a Greek letter.
One legacy of Flamsteed’s atlas which is sometimes overlooked is the sequence of smaller popular atlases that it inspired: Jean Fortin’s Atlas Céleste in France (1776 and 1795), Johann Bode’s Vorstellung der Gestirne in Germany (1782 and 1805), and Alexander Jamieson’s Celestial Atlas in England (1822), all of which in turn had their own imitators. See my page on Old Star Atlases for more on this Flamsteed tradition.
Flamsteed’s catalogue and atlas set new standards in astronomy, and I have used his atlas as one of the sources for illustrations on these pages. The other main source is the greatest of the old-style pictorial star atlases, Uranographia, published in 1801 by the German astronomer Johann Elert Bode, director of Berlin Observatory. (It actually appeared in five parts from 1797 onwards, but 1801 was the completion date.)
Bode’s Uranographia was the first atlas to depict virtually all the stars visible to the naked eye (i.e. down to sixth magnitude), plus a fair selection of those down to six times fainter (eighth magnitude). Over 17,000 stars are plotted, taken from the observations of various astronomers including Flamsteed, Lacaille, Lalande, and Bode himself. To accompany the atlas, Bode produced a catalogue called Allgemeine Beschreibung und Nachweisung der Gestirne, also published in 1801.
Uranographia was also the first major star atlas with boundary lines drawn between the constellations, albeit vague and ill-defined, unlike the rigorous modern boundaries. Even Flamsteed, normally so punctilious, had been entirely unspecific about the extent of each constellation on his charts.
Bode intended the Uranographia to be comprehensive and he certainly succeeded, for in addition to charting a greater number of stars than any previous cartographer he also depicted more constellations – over 100 of them (for a complete list see here). Among them were five constellations making their debut on this atlas: Felis and Globus Aerostaticus were both suggested by Lalande during the preparation of the atlas, while Lochium Funis, Machina Electrica, and Officina Typographica were invented by Bode himself. None of these five survived the test of time, however.
Bode’s Uranographia marked the end of an era. Thereafter, astronomers placed decreasing emphasis on the fanciful (and physically meaningless) constellation figures of the Greeks, concentrating instead on the exact measurement of position, brightness, and physical properties of the stars.
End of a tradition
In the transition from classical to scientific mapping that occurred during the 19th century one atlas stands out: the Uranometria Nova of the German astronomer Friedrich Wilhelm August Argelander (1799–1875) published in 1843. In this the constellation figures, printed in red, were reduced to shadowy insignificance by comparison with the stars. This same two-colour style was followed by Argelander’s countryman Eduard Heis (1806–77) in his Atlas Coelestis Novus of 1872. These atlases were the standard references for professional astronomers of the day, and their choice of constellations helped establish the eventual list of 88 adopted by the International Astronomical Union in 1922.
By the end of the 19th century, two thousand years of Greek tradition had finally given way to the facts-and-figures approach of astronomical census-takers and statisticians. Where the ancient Greeks imagined their gods and heroes populating the sky, modern astronomers have discovered the existence of an equally fantastic pantheon of objects with names such as red giants, white dwarfs, Cepheid variables, pulsars, quasars, and black holes.
© Ian Ridpath. All rights reserved