Constellation
2 of the 7 encyclopedias on this shelf carry an entry for Constellation. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a group or configuration of stars, within certain boundaries, to which a definite name has been assigned, the name being generally expressed in its Latin for the sake of international convenience and of exactness. This grouping is almost entirely artificial, though some of the configurations bear some resemblance to the object indicated by the name. History. Before the invention of almanacs the risings and settings of the constellations were looked to by husbandmen, shepherds, and sea-faring men as the landmarks of the seasons, and of the weather which each season was expected to bring. The earliest description that we have of the constellations is the poem by Aratus, called "The Phenomena of Aratus," about 280 b. c. The Greek sphere used by Hipparchus, 125 b. c., appears to be the earliest known accurate representation of the positions and magnitudes of the stars, and upon this they were grouped into 48 constellations. We know of this work through the description of it in Ptolemy's "Megale Syntaxis, ," A. D. 170. This was translated by the Saracens into Arabic, A. D. 813-832, and miscalled by them the "Almagest," and it is principally through translations of this work that we know of these 48 original asterisms. Various astronomers have since then added a host of others, but most of these have fallen into disuse. Lettering the Stars. In 1603 Bayer, in his "Uranometria," immortalized him self by the happy thought of assigning letters to the individual stars of each of the 48 constellations of the "Almagest" beginning with the Greek alphabet and following approximately the order of brightness of the stars, and then using the lower-case Roman letters where needed to complete any constellation. Some confusion has arisen, especially in those extending far toward the S., in trying to identify all of Bayer's lettered stars. Argelander's "Uranometria Nova" is, however, accepted to-day, with a few trifling exceptions, as the correct interpretation of Bayer. Lacaille, at the Cape, 1751- 1752, extended the same system to the southern constellations, and was also compelled to revise the lettering of a few of Bayer's most southern ones, which were very inaccurately delineated. As far N. as his work extended, to +10° of declination, Dr. Gould also assigned letters in the constellations still unlettered, Monorceros, Scutum, and Sextans. In the northern constellations added by Hevelius, or between his time and Ptolemy, and which had not been lettered, Bailey assigned a few Greek letters when publishing the " B. A. C." (British Association Catalogue) in 1845. These letters will probably stand in any future revision of the northern heavens, though they are not very generally used by astronomers to-day. It should also be noted that the last letters of the capital Roman alphabet, beginning with R, are reserved for the variable stars. This has been agreed upon since Argelander's time, and has compelled the abandonment of several such letters assigned by Lacaille in the southern heavens to stars that are not variables. Flamsteed's numbers in each constellation of the stars observed by him are also extensively used as a system of naming individual stars. These numbers refer to the order in which the stars occur in each constellation in his "Catalogus Britannicus." Other early catalogues of stars arranged in this way by constellations are often used as a means of naming individual stars, especially that of Hevelius, a capital H being used in this case. These numbers refer, not to the arrangement of the stars in Hevelius's original "Prodomus Astronomiӕ" (1690), nor to Bailey's edition of it in the 13th volume of the "Memoirs of the Royal Astronomical Society," but to Flamsteed's edition of the catalogue as published in the third volume of the "Historia Cælestis Britannica," London, 1725, and considerable confusion has at times arisen from ignorance of this fact.
Aiton's Encyclopedia (1910)
a group of stars. One observing the sky on a clear night cannot fail to observe that the bright stars form more or less noticeable groups. The best known to young people is perhaps that of the Great Dipper, the outer stars of which point to the pole star . The belt of stars through which the sun appears to move annually was divided into twelve groups or constellations, probably by the Babylonians, certainly prior to the earliest extant history. The earliest works on the subject, of which we have any knowledge, were written in the fourth century before Christ. The earliest astronomical writing that has been preserved is a star catalog called the Almagest. It was prepared by Ptolemy, the Greek professor of astronomy at Alexandria, about 120-150 A. D. His catalog contains over a thousand stars divided into forty-eight constellations. This ancient grouping has never been disturbed seriously. Astronomical maps of the present day adopt the groups and use the names given by Ptolemy. The principal additions are those in the southern hemisphere , which were not known to the Greek writer. The entire sky has now been plotted off and given names. In all, the additions have brought up the number of constellations to eighty-nine. Most of the names adopted by Ptolemy were derived from the Greek mythology. See Orion ; Cassiopeia ; Charles'S Wain ; Berenice'S Locks