Uranometria is the title court of the Catalog of stars carried out by the German Astronome Johann Bayer. He was published in Augsburg (Germany) in 1603 by Christophorus Mangus under the complete title Uranometria: omnium asterismorum continens schemata, nova methodo delineata, aereis laminis expressa. ( litt. “Uranometria, containing the charts of all the Constellation S, drawn according to a novel method and engraved on plates of Copper”.

The word “Uranometria” comes from the Greek oυρανός (sky), which gives also its name to Uranie, MUSE of the Astronomie in the Greek Mythologie. The suffix “metria” comes from the Latin “measurement”, thus “Uranometria” means “measurement of the sky”, by analogy with “geometry” which étymologiquement means “measurement of the Ground”.

Uranometria is the first catalog to cover the totality of the celestial Sphère.

Genesis of the Uranometria

Before Johann Bayer, the development of the celestial charts was mainly guided by esthetic and astrological concern, the positions of stars being indicated, and even not adjusted most of the time to yield with the requirements of form of the figures stylized that the constellations were judicious to represent, in alarming relatively little astronomical exactitude. This tradition, generally based on the catalogs altogether rather not very precise of Ptolémée and Al-Been enough, will perdurera during all the Moyen-âge and the Renaissance, until the publication of the Uranometria , which will benefit from the best star catalog available at the time of its drafting, that of Tycho Brahé.

This catalog contains 1005 stars, located with a precision about the Minute of arc. With died of Brahé in 1602, it was still not published, but of the manuscripts are in circulation in all Europe since 1598. No one really does not know how Bayer, magistrate in Augsburg and which was affiliated at no learned society of the time got a specimen of it, always is it that this catalog of a precision ever reached before will be used as a basis for the realization of its celestial atlas.

However, the tables of Brahé, measured since the Denmark, do not list the most southern stars. To carry out the 49e board of his atlas, which introduces 12 new constellations of the Southern hemisphere, Bayer will use a catalog produced by two navigators Dutch, Pieter Dirkszoon Keyser and Frederick de Houtman between 1595 and 1597, which them even had begun again and improved the observations of their predecessors Amerigo Vespucci and Andrea Corsali, as well as the notes of Pedro de Medina. This catalog of 135 stars proves however definitely less precise than that of Brahé, positions of stars having sometimes errors of almost two degrees (according to the legend, they would have observed and measured the sky since the Hune of their Navire).

The Uranometria contained much more stars than all preceding the catalogs, its exact number being difficult to estimate precisely because many stars are drawn without being named.

Designation of Bayer

See also: Designation of Bayer

Into the Uranometria , Bayer introduces a new star nomenclature, from now on known under the name of Désignation from Bayer, and which is always used today for stars concerned.

For the publication of this atlas, when one wanted to indicate a star in particular, it was necessary to describe its position in the constellation: “the star shining on the southern foot of Andromède” or “the left shoulder of Orion” for example, but these descriptions were often ambiguous.

This new system invented by Bayer consists in allotting to stars of a given constellation of the Greek letters in the decreasing order of their glare. Thus, the most brilliant star has designation Alpha (α), following Bêta (β), and so on with the 24 letters which the Greek alphabet comprises. However, average the techniques of the time not allowing to precisely classify stars in the order of magnitude, Bayer gathers each one of them in six different “classes”, the stars 1st lowest magnitude being most brilliant and those 6th magnitude.

Then, inside the same class, Bayer does not seek any more to classify stars by magnitude but rather according to their position in the constellation, leaving the head in general to arrive at the feet (or with the tail). Thus, in the constellation of Orion for example, Bételgeuse (α Orionis), which represents the shoulder of Orion, is classified before Rigel (β Orionis), the foot, although the latter is most brilliant of both.

The stars represented on the 49e board (that introducing the 12 new southern constellations of Keyser) however did not receive designation on behalf of Bayer, sign probably of the poor quality of information it had. Those accepted their designation later only 160 years, in 1763, by Nicolas-Louis de Lacaille.

Description and contained

In the original edition of 1603, the work (of which the largest sheets measure 38x28 cm) includes/understands 56 layers. The illustrations were initially engraved on copper plates by the artist augsbourgeois Alexander Mair (approx. 1562 - 1617) before being reproduced on paper. The layers break up as follows:

*un for the title page

*un for the dedication *deux

for the foreword

*48 for the charts of the constellations of Ptolémée and the tables associated

* another for the 12 new southern constellations *deux

for the planispheres with the two hemispheres

*et finally a virgin layer at the end of the work.

The layers are numbered starting from the first constellation (the Petite Ourse), by using an alphanumeric code based on the 24 letters of the Latin alphabet (the J and U did not form part of it at the time). Thus, the first layer is numbered (recto-back) has, the second B, then C until the twenty-fourth. Then classification sets out again of has but by doubling the letter and decreasing its size, that is to say Aa for the twenty-fifth layer, then finally Aaa for fifty-and-unième. Constellation S of Ptolémée with some modifications and additions (see below). The 49e page introduces 12 new constellations (see below) southern sky, invisible unknown factors of Ptolémée because since the Mediterranean basin because of their too low variation. The two last pages are Planisphère S representing the celestial hemispheres north and south in their totality (“ Synopsis coeli superioris borea ” and “ Synopsis coeli inferioris austrina ”, respectively). -->

Title page

The engraving of the title page shows an architectural reason, the complete title being registered in the center of the illustration. Atlases and Héraclès are represented each one on a pedestal on both sides of the title, these pedestal carrying the inscriptions “ Atlanti vetvstiss astronom magistro ” ( litt. “Atlas, the first to have taught astronomy”) and “ Herculi vetvstiss astronom discipulo ” ( litt. “Hercules, the first student in astronomy”).

The higher stringcourse represents several ancient Greek divinities. In top on the left is Hélios (the Sun), and in the center Eternity on its celestial tank, capped of a crown of stars and holding two lions leaves some. Séléné (the the Moon) is represented in top, covered on the right with a spangled cape.

Lastly, the lower part of engraving is made up of a representation of the Capricorne, as well as sight of Augsburg, city in which the work was published

48 constellations of Ptolémée

The constellations are presented by decreasing order of variation, starting with the Petite Ourse, the 12 constellations of the Zodiaque appearing 22e (Bélier) with the 33e position (Poisson), the 15 following constellations being located at the lower part of the plan of the ecliptic .

Each illustration is surrounded by a scale in degree S to make it possible to determine the position of each star with a precision of a fraction of degree. These rules are numbered all the five degrees, and a line joined the higher and lower rules all the 30 degrees. Lastly, the scale is repeated throughout the ecliptic . A thick dark band, extending between 8° with north and 8° in the south from the ecliptic, represents the zone in which the Planet S can be observed. According to the habit of the time, an artistic drawing of the constellation appeared in filigree of stars of the constellations. For an unknown reason, several human characters representing of the constellations appear of back and not of face (perhaps because the celestial spheres of this time showed the characters of face, whereas Uranometria showed the constellations seen by an observer located at the center of the celestial sphere and not outside this one, as it is the case with a sphere). So certain star names explicitly referring to their position in the constellation have a name in dissension with the illustration. For example, the illustration of the constellation of Céphée watch the character of back, the most brilliant star (α Cep/Alderamin) being of this fact on the level of its left shoulder, whereas étymologiquement its name means “the right-hand man”. In the same way, in the constellation of Orion (opposite) the position of back of the hunter puts Rigel, located in bottom on the right of the constellation, on the level of its right foot whereas étymologiquement its name corresponds to the “giant left foot”.

Each chart of constellation is preceded by a table containing the nomenclature, the description and the magnitude of the stars which composes it. Unfortunately, the first edition of work had a serious problem: the table and the chart of a constellation were printed on the same layer, one with the recto the other with the back, it thus became impossible to consult both simultaneously, reducing thus largely the interest of the unit. In all the following editions (starting from 1624), the back of the charts was left white, and the separately printed tables.

12 southern constellations

The 49e illustration of the work introduces 12 new southern constellations mentioned by the navigators of the end of the 16th century Pieter Dirkszoon Keyser and Frederick de Houtman between 1595 and 1597. They “were to some extent officialized” in the Uranometria .

The catalog of Keyser and Houtman being however definitely less complete than that of Brahé used for the northern hemisphere, Bayer names stars of this board by using the new designation which it created for the 48 preceding constellations, but is satisfied to represent stars with dimensions appreciably different according to the magnitude from one or the other. In fact, this board is not preceded by a nomenclature of stars being present there, only of one short list presenting the new constellations:

• Bird of paradise
• Chameleon
• Sea-bream
• Crane
• male Hydre
• Indian
• Fly (at the time, the Bee)
• Peacock
• Phoenix
• southern Triangle
• Toucan
• Flying fish

One also notes the presence on this board of the Grand and the Petit Cloud of Magellan: saw are represented there like true clouds, thus contrasting with the more realistic drawing of the Milky Way near.

List modifications of the constellations in the Uranometria

These modifications consisted in dividing a constellation into a great of the same constellation name than the initial constellation and smaller.

• Centaur, cut out in Centaur and Cross of the South (the Throne of César in Antiquity). The Cross is mentioned in the text (cf, page of left), but does not have corresponding entry nor is not described on the 49e illustration.

• Lion, cut out in Lion and Hair of Bérénice, which appears in fact in the page devoted to the constellation of the Bouvier in the shape of a sheaf of corn, cf, the name being on the other hand mentioned in the text (, page of left). The constellation existed since Antiquity, but did not appear in Almageste de Ptolémée.
• southern Poisson, cut out in southern Poisson and Crane, cf, the Crane appears on the 49e illustration.
• Sagittarius, cut out in Sagittarius and southern Crown, cf, page of left, the southern Crown is described on the 47e illustration. The constellation existed already time of Ptolémée, but had been thereafter abandoned.

Bayer thus changes the number of constellations to 62: the 48 of Ptolémée to which 12 qu are added ' it gives in the southern hemisphere, plus Hair of Bérénice and the Cross of the South. These constellations cover all the vault of heaven. To arrive at the 88 constellations now recognized by the international astronomical Union, various constellations will be added in the empty zones left by Bayer. The principal contributors will be Nicolas-Louis de Lacaille, Petrus Plancius and Johannes Hevelius with 17th and 18th centuries.

Later editions

After the original publication of 1603, the Uranometria will be republished at least three times, in 1627, 1661 and 1697. The edition of 1627 is rather particular: it was published little of time after the death of Johann Bayer with for new title Coelum Stellatum Christianus (Christian sky). In fact, Bayer had assisted one of his friends, Julius Schiller, in his company of evangelization of the night sky. The two men had taken again the original version by correcting certain errors, but especially by replacing the whole of the pagan constellations by characters or biblical objects. The twelve constellations of the Zodiaque were thus replaced by the twelve Apôtre S, the Navire Argo by the Arche of Noah, the river Éridan by the Red Sea and so on. This attempt will have however only little success and there remain about it nothing any more today.

See too

• Almageste
• Catalog of stars

External bonds

• Reproduction of all the illustrations of Uranometria

• Bayer 1661 and Image high-resolution of certain illustrations

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