December 5, 2007

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Sheets and Quads

Sheet A6 of the System of Lunar Craters

One detailed, relatively accurate and even official map of the Moon is poorly known and now almost no longer available. I refer to the 44 sheets that accompanied the System of Lunar Craters catalog published in quadrants from 1963 to 1966 at the University of Arizona. I was a coauthor of the System, working under Dai Arthur, and was intensely involved in the making of the maps. The purpose of the maps was to illustrate the IAU nomenclature that we heavily revised, but also they were part of the accuracy check of the crater cataloging. As we completed cataloging each quadrant (one fourth of the visible face of the Moon) we plotted (pre-computer, by hand) the coordinates of each crater on sheets of graph paper at the correct position and with the right diameter and degree of ellipticity (using plastic templates to draw the ovals). And then came the hard part, comparing each part of the map with photographs to see if each crater had the correct positional and size relationship with its neighbors. We also checked to see which one overlapped others so the map would accurately depict relative ages. I remember that the map making and checking took nearly as long as the crater measuring. Alice Agneiray drafted the final charts, 11 for each quadrant, using the LeRoy lettering system to print the nomenclature. Each map had a rectangular (direction cosines) grid and boundary areas giving names of adjacent craters. The charts were numbered - the one above is A6 - using the same arrangement as the fields of the Photographic Lunar Atlas. After the four quadrant catalogs and maps were finished, Alice assembled the 11 sheets from each catalog into a single quadrant map, identical to the individual sheets with the addition of a stipple pattern to indicate the maria. The University of Arizona published these maps for a while, but at some time after I left Tucson they were given to Sky and Telescope to sell. S&T no longer has them listed but a recent call to their catalog company revealed that some are still in stock, but too few to advertise. I just ordered a set of these historical maps and encourage you to as well!

Chuck Wood

Technical Details:
Apparently there is a discussion as to why the 44 sheets are called quadrant maps. It’s simple. Each set of 11 map one lunar quadrant.

Related Links:
Rükl plates 59 & 60
The only place the System of Lunar Craters maps seem to be online is at the GRL website, thanks to Charlie Kapral.

Yesterday's LPOD: Too Much Data?

Tomorrow's LPOD: Unsolicited Advice


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