IAU XII News Report

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IAU XII News Report

(this is a transcription of a portion of an article about the IAU's 1964 Meeting in Hamburg by Managing Editor William E. Shawcross on page 342 of the December, 1964 issue of Sky and Telescope)

Lunar Nomenclature

All lunar observers — professional and amateur — feel the need of convenient, unambiguous, and internationally used labels for several thousand of the more conspicuous surface features of the moon. Our present system is a traditional one that grew piecemeal. Several hundred of the larger craters were named after scientists by Riccioli about 1650, and hundreds of others have been similarly named since. About 1835 Mädler introduced the practice of giving letters to smaller craters near a large one, so that we have Archimedes A, Archimedes C, and so on. Much confusion existed in the 19th and early 20th centuries when many workers were mapping the moon independently, each adding more names and letters and changing others. To cure this confusion. Mary A. Blagg and K. Müller compiled a unified nomenclature, which was published in both catalogue and atlas form. Their system was officially adopted by the IAU in 1932.

Since then, some shortcomings of the system of Blagg and Müller have been realized. and a special subcommission (16a, nomenclature and cartography of the lunar surface) met at Hamburg to consider improvements. Everybody agreed that Blagg and Müller's designations should be preserved as far as possible. with only necessary changes to avoid ambiguities and inconveniences. D. W. G. Arthur (Lunar and Planetary Laboratory) made these specific suggestions, which were approved.

1. A small crater inside a large one (such as Ptolemaeus A inside Ptolemaeus) should not receive an individual name.

2. Individual names should not be given to both members of a close pair (such as Messier and W. H. Pickering) because of the ambiguity this produces in neighboring lettered craters.

3. Cases like Hainzel P should be corrected, since another named crater (Mee) lies between it and Hainzel.

4. Initials in crater names should be avoided. For example, each of two famous brothers, E. C. Pickering and W. H. Pickering, has a crater named after him. In view of point 2, Mr. Arthur suggests that the former crater be called simply Pickering, and that the latter revert to its historic designation Messier A.

Moreover, said Mr. Arthur, lunar cartography has changed drastically in the last 10 years. In the high-quality, large-scale charts now being prepared by professional cartographers, map projections are used that avoid undue compression near the moon's limb. This affects nomenclature by "moving craters apart" and also creates wide areas with no named objects. Therefore, in the Air Force Lunar Charts and in the new Lunar Quadrant Maps being prepared at the Lunar and Planetary Laboratory, about 60 new names have been added to occupy strategic locations near the limb. These names have been carefully chosen to honor famous scientists of many countries.

There are still outstanding problems in lunar nomenclature. No satisfactory system for naming rilles exists yet, nor for domes. And what is to be done when designations are needed for large numbers of craters smaller than the two-mile diameter limit of today's nomenclature? Mr. Arthur noted that in crowded regions the present system makes some use of designations like Clavius CA and CB for lesser neighbors of Clavius C. He proposed that still lesser features could be called ABC, ABD, or possibly AB1, AB2, and so on. J. Hopmann of Vienna mentioned his preference for coordinates instead of names, and Dr. Kuiper suggested name-number combinations, such as Copernicus 302. The choice among these systems has been left to the future.