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Becvar's atlases


by Lubor Kresak
published in Kozmos XIV, No. 5, 147-147 (1983)
English translation by Lubos Neslusan

Atlas Coeli The best-known and most used, drawn astronomical atlas all over world is the Becvar's Atlas Coeli Skalnate Pleso. In the coordinate system referred to equinox 1950.0, all stars brighter than 7.75 magnitude are included. The plotting is gradated by the magnitude in 16 large maps of the atlas in the scale of 1° = 0.75 cm. There are specifically marked the visual and spectroscopic double stars, multiple systems, novae, supernovae and the brightest radio-sources; then globular and galactic clusters, galaxies and extragalactic nebulae up to 13th magnitude, the shapes of larger diffuse and dark nebulae, the shape of the Milky Way, the Ecliptic, the Galactic equator and the international borders of constellations. In contrast to other atlases, Atlas Coeli is unique mainly because of the comprising of all planar and diffuse sources being visible in a telescope of a diameter up to 20 cm. Due to this fact, the atlas became an ideal implement for, e.g., the search for comets, i.e. for the work, which motivated the creation of the atlas in part. The high perfection and clearness of maps have been a cause, why the atlas has served as a necessary implement at night work during not less than three decades, in the professional observatories all over the world as well as at the observations by the pretentious amateur astronomers.

The atlas was created on the basis of various astronomical catalogues and about ten photographic atlases in the period of 1947-1948. It had been created by a collective group associated in a large part by the students, who had stayed practising at the Skalnate Pleso Observatory during their holidays in these years. The whole conception and final plottings of the atlas, including the descriptions, are completely the work of Dr. A. Becvar himself. One can imagine the extension of the work on the basis of the fact that there had to be drawn and checked, by a dictate, the positions of about 35 000 objects into the coordinate net. Including the overlapping regions, the sum of objects, together with repeating of some on two or three maps, was almost 50 000. To plot each of the objects, there was necessary to choose one of 20 patterns in a stencil and to set the correct position of it. A lot of hard work had been necessary to complete the basic Boss Star Catalogue, which had been the most appropriate for this purpose that time but, unfortunately, it had not been quite complete up to the limiting magnitude of the plotted stars. Here, the need to read almost a quarter of million of stars in the Henry Draper Star Catalogue occurred, whereby there was not only necessary to identify the stars absenting in the Boss catalogue, but also a re-calculation of their positions taking into account the 50-year precession had to be done.

The atlas was, at first, published by the Czechoslovak Astronomical Society in 1948. Soon after, the Catalogue followed. It was issued as the second volume entitled the Atlas Coeli II. This contained various data on more than 12 000 chosen objects (common stars up to the 6.25 magnitude only, the complete set, as in the maps, of other objects). A six-colour improved version of the atlas was published by the publishing house of the Czechoslovak Academy of Sciences in 1956. The copy-right to publish the atlas outside the Czechoslovakia was bought by the Harvardian "Sky Publishing Corporation", which advertized it in its most spread popular scientific journal "Sky and Telescope". Under copy-right of this corporation, the atlas has been published in a series of editions: from a luxurious to a common, reduced in size, with white stars on black background. By the requirement of the author, royalties were met in the form of special astronomical photographic plates, which significantly improved the efficiency of the telescopes of the Skalnate Pleso Observatory for several next years.

Dr. A. Becvar went on in the creation of atlases after he was retired and lived in his birthplace in Brandys nad Labem. The result was represented with three celestial atlases in a scale of 1° = 20 cm: Atlas Eclipticalis (the celestial region between -30 and +30° of declination on 32 maps), Atlas Borealis (the celestial region northwards from declination of +30° on 24 maps), and Atlas Australis (the celestial region southwards from declination of -30° on 24 maps). These atlases were considered for more specific purposes: the choice of plotted stars is not limited by their brightness but by the knowledge of their precise positions and proper motions; stellar clusters and nebulae are not plotted but six-colour press is utilized to distinguish 6 basic spectral classes of the stars. Also these atlases have been spread all over the world by the Sky Publishing Corporation. They have served mainly for the choice of reference stars in the photographic astrometry and photometry. They were especially utilized in the first phase of position measurements of artificial satellite.

Perhaps, the most significant appreciation to Dr. A. Becvar (1901-1962) for his atlases has been that a crater on the Moon was named by his name. It is certainly worthy of admiration, when a unique work, Atlas Coeli Skalnate Pleso, is recognized, in a certain topic, to be the most used scientific aid during entire three decades. So late as in 1981, a successful concurrent, Atlas Tirion Atlas 2000.0, appeared. It will probably take the role of the Atlas Coeli after the change of equinox, from 1950.0 to 2000.0. Tirion's atlas has its scale enlarged to 1° = 1 cm. It consists of 26 instead of 16 maps, and it contains stars up to 8.0 magnitude, i.e. about one third more than the Becvar's atlas. A look at this concurrent, a generation younger and from the era of computers, is perhaps the greatest compliment which the Atlas Coeli Skalnate Pleso could ever receive: almost everything, up to the marks for various types of objects, division of scales, and the type of script are taken from the Atlas Coeli. What a little improvement of this work was necessary after 30 years!


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