SkyEye

The Dog-star and Aldebaran, pointing to the restless Pleiades, were half-way up the Southern sky, and between them hung Orion, which gorgeous constellation never burnt more vividly than now, as it soared forth above the rim of the landscape. Castor and Pollux with their quiet shine were almost on the meridian: the barren and gloomy Square of Pegasus was creeping round to the north-west; far away through the plantation Vega sparkled like a lamp suspended amid the leafless trees, and Cassiopeia’s chair stood daintily poised on the uppermost boughs.
— Thomas Hardy, "Far From the Madding Crowd", 1874

A constellation is a picture in the sky, and societies around the world grouped the stars into figures meaningful to them and their culture. Many of these familiar patterns of stars come to us from prehistoric times when humans first looked up into the night sky and tried to make sense of it. Others are of more recent origin, concocted when European explorers ventured far into the southern hemisphere.

The constellation charts are drawn in colour on a dark background. Coloured circles of varying radii are used to represent stars. The larger the circle, the brighter the star. Binary and multiple star systems that appear as a single object to the naked eye are represented by their combined magnitude. The colours represent the spectral types (surface temperatures) of the stars, with blue being the hottest and red the coolest. A selection of other interesting celestial objects are drawn in green, with thick green lines representing the figures of the constellations. Star positions (epoch J2000), magnitudes and colours are taken from the Smithsonian Astrophysical Observatory Star Catalog. The limiting stellar magnitude is +6.5 (except for very faint but noteworthy stars) but there is no limiting magnitude for other objects.

Modern Constellations

Today, the International Astronomical Union is the sole authority for assigning designations and names to celestial bodies and in the early twenthieth century, they divided up the sky into 88 sections. These sections are irregular in shape and size as the IAU has tried to maintain ancient constellation boundaries as much as possible.

Extinct Constellations

Before the twentieth century, when the International Astronomical Union recognised 88 constellations and established their formal boundaries, constellations came and went, with astronomers and cartographers adding or renaming constellations with every new atlas published. Some honoured new-fangled inventions (the electricity generator, the hot air balloon), some flattered the important leaders of the day (Charles Ⅱ, George Ⅲ), some might even have been suggested as a joke (the pangolin?), but in the end, most of them did not survive to the modern day.

The Christian Sky

There have been attempts to 'Christianise' the celestial sphere for as long as there has been a Christian religion. Perhaps the best known member of this movement is Julius Schiller, a German lawyer who based his 1627 star atlas Coelum stellatum Christianum on Johann Bayer's earlier work. In it Schiller replaced the zodiacal constellations with the twelve apostles, the northern constellations with New Testament figures and the southern constellations with Old Testament figures. However, the saints were no match for the pagans and the snappy new names never caught on. As John Hill (Urania, 1754) said in his description of Cygnus:

Schickard, Schiller, and their followers, that they may make [Cygnus], as well as the other constellations, preserve some part of the scripture history, call this the Cross, or the Cross of Christ, and St. Helena the hinder part of it. But these have few followers. It is obvious to all men what confusion must attend altering the figures of the constellations.

Key

For the two centuries between 1600 and 1800, celestial cartography flourished in Europe. This was its golden age. Atlases became more elaborate, more inclusive and more accurate. Perhaps the four star atlases that epitomised the age were Uranometria: omnium asterismorum continens schemata, nova methodo delineata, aereis laminis expressa (Johann Bayer, 1603), Firmamentum Sobiescianum, sive Uranographia (Johannes Hevelius, 1690), Atlas Coelestis (John Flamsteed, 1729) and Uranographia sive Astrorum Descriptio (Johann Elert Bode, 1801).

1. Κλαύδος Πτολεμαι̃ος (Claudius Ptolemy), Almagest (second century CE)
2. Johann Bayer, Uranometria: omnium asterismorum continens schemata, nova methodo delineata, aereis laminis expressa (1603)
3. Petrus Plancius, celestial globe of 1612
4. Johannes Hevelius, Firmamentum Sobiescianum, sive Uranographia (1690)
5. John Flamsteed, Atlas Coelestis (1729)
6. John Hill, Urania, or a Compleat View of the Heavens (1754)
7. Nicolas-Louis de Lacaille, Coelum Australe Stelliferum (1763)
8. Johannes Elert Bode, Uranographia sive Astrorum Descriptio (1801)
9. Giuseppe Piazzi, Praecipuarum Stellarum Inerrantium Positiones Mediae Ineunte Saeculo ⅩⅨ (1814)
10. Alexander Jamieson, A Celestial Atlas: Comprising A Systematic Display of the Heavens in a Series of Thirty Maps Illustrated by Scientific Description of their Contents, And accompanied by Catalogues of the Stars and Astronomical Exercises (1822)
11. Eugène Delporte, Dèlimitation scientifique des constellations (1930)
12. Richard Hinkley Allen, Star Names: Their Lore and Meaning (Dover reprint, 1963)