Constellation Maps

An example of a constellation type of star map is shown in Figure 1.1. This plate is from a celestial atlas first published by Fortin in 1776 and shows the sky around the central constellation of Cygnus the swan. Our eye is first drawn to the beautiful constellation images, here shown in vivid color. In some star atlases, the color was original, but in most cases (such as this one) color was added later to enhance the beauty and decorative quality of the plates. Further perusal of this plate reveals that the names of the constellations are in the French language, indicative of the French origins of the atlas from which the plate comes. According to the title, four constellations are featured: la Lyre (Lyra the lyre), le Cygne (Cygnus the swan), le Lezard

LA I.YRE, Ll\ (.TUN 1:'., LE I.KZAKtD. I.I. KKNARI), "

LA I.YRE, Ll\ (.TUN 1:'., LE I.KZAKtD. I.I. KKNARI), "

Lyra Constellation Map

Figure 1.1. View of several northern constellations, taken from the third French edition of Fortin's Atlas Céleste de Flamsteed, 1795.15.7 x 20.6 cm. Note the constellations of Lacerta ("le Lezard", which looks more like a dog than a lizard); Cygnus (flying in the Milky Way); Lyra (with the bright star "Wega''); and Vulpecula ("le Renard'') clutching in its jaws Anser ("l'Oye", which no longer exists). See also Color Section 1.

Figure 1.1. View of several northern constellations, taken from the third French edition of Fortin's Atlas Céleste de Flamsteed, 1795.15.7 x 20.6 cm. Note the constellations of Lacerta ("le Lezard", which looks more like a dog than a lizard); Cygnus (flying in the Milky Way); Lyra (with the bright star "Wega''); and Vulpecula ("le Renard'') clutching in its jaws Anser ("l'Oye", which no longer exists). See also Color Section 1.

(Lacerta the lizard, looking here more mammalian that reptilian), and le Renard (Vulpecula the fox). Clenched in the jaws of Vulpecula is a separate constellation, l'Oye (Anser the goose). Lyra and Cygnus are among the 48 traditional constellations that have been with us for some 2,000 years, since ancient Greek times. In contrast, Lacerta and Vulpecula are "new" constellations that were introduced by the famous Polish astronomer Johannes Hevelius in 1687. Although these two constellations are still with us today, Anser is not, being a victim of the actions of the International Astronomical Union in 1922 when it purged the sky of many constellations in an effort to standardize their number and to discourage the actions of astronomers eager to honor patrons or celebrate events by inventing constellations for their star atlases (the I.A.U. settled on 88 constellations, which are now considered official). So, throughout history, constellations have come and gone, and what one sees in a given star atlas reflects what was current in the mind of its creator.

But Figure 1.1 shows more than constellations. Note the presence of two grid-like coordinate patterns, one using dotted lines and one solid lines. The first was based on an imaginary line in the sky representing the path of the Sun called the ecliptic. The second was based on an imaginary line in the sky that was a projection of the Earth's equator called the celestial equator. These will be described more fully later on, but for now the point to note is that these two systems allowed any object in the sky to be "mapped" according to the coordinate system being used. This was a major advance over pre-Renaissance systems, where the location of heavenly bodies was in reference to their location in a constellation (e.g., "the star at the end of the right foreleg'' or "the planet at the tip of the tail'').

Plates such as this one were often used to accompany a star catalog, which gave detailed information about stars such as their location in the sky, brightness (or magnitude), etc. Some of this information could be incorporated in the constellation map. For example, note that according to the scale at the bottom, Vega is a magnitude 1 star since it is indicated on the plate by a large gold symbol. In contrast, the star near the tip of Lacerta's nose is much dimmer at magnitude 5. Also shown in the plate are the locations of various nebulae, the supernova of 1670 (near Vulpecula's upraised ear), and the cloud-like Milky Way running diagonally from upper left to lower right.

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