The Marginal Zone of the Moon
by Richard P. Wilds (and Chester B. Watts, deceased)
The rich history of mapping the edge of the Moon, and the interactions of those efforts with lunar occultations, is described well in this Word document written by Richard Wilds. Extensive background information is given before recounting much of the information published by C. B. Watts in Astronomical Papers prepared for the use of the American Ephemeris and Nautical Almanac, Volume XVII, "The Marginal Zone of the Moon", United States Government Printing Office, Washington, 1963, called simply "Watts' charts" for easy reference. Unfortunately, this publication has been out of print for many years, so much of its contents are given in the Word file, and many of its figures are given below. The P/D charts are copied here, with the names of the craters and other features of the marginal zone added. Also below are some annotated Clementine maps, other figures of the marginal zone, and some grazing occultation reductions showing the features that caused the observed events.
Annotated P/D Charts
Read the Word file for an explanation. Chart 1, P = 0 to 30 Chart 2, P = 30 to 60 Chart 3, P = 60 to 90 Chart 4, P = 90 to 120 Chart 5, P = 120 to 150 Chart 6, P = 150 to 180 Chart 7, P = 180 to 210 Chart 8, P = 210 to 240 Chart 9, P = 240 to 270 Chart 10, P = 270 to 300 Chart 11, P = 300 to 330 Chart 12, P = 330 to 360
Other Figures from Watts Charts
Libration Chart Example Lunar Limb Example Lunar Limb Measuring Engine
Other Figures
South Pole Drawing #1 South Pole Drawing #2 Annotated Clementine North Polar Map Annotated Clementine South Polar Map Lunar Prospector Impact Site Map 1852 Graze seen by Gillis, showing lunar features Nov. 3, 1992 graze predicted profile showing lunar features Maia graze deep in Cassini region showing lunar features The Watts charts were made at the dawn of the computer age with older equipment that didn't easily allow saving the information in computer-readable form, so that was not done. After the charts were published, the Royal Greenwich Observatory manually scanned the charts with a "pencil-following" device that recorded the x,y coordinates of the chart contours, as well as of grid points on the charts for registration of the results. L. V. Morrison and R. J. Martin described this work in "A digitised version of C. B. Watts' charts of the marginal zone of the moon" in Earth, Moon and Planets, Vol. 2, pp. 463-467. The data were further processed at the U. S. Naval Observatory to put the data in a more useful form for lunar occultation computations, and this dataset has been reformatted and refined for use by current software. IOTA member David Herald worked to make the dataset available at the astronomical data center in Strassbourg, France, as described here. Richard Wilds, astromaster@sunflower.com __________________________________ Information about recent lunar mapping efforts, and how they might interact with analyses of occultation observations, are given in messages by Anthony Cook and Anthony Mallama. David Dunham and Richard Wilds have some comments about the new Goldstone radar map of part of the south polar area here. This Web site was prepared by David Dunham on 2008 February 26 using material developed by Richard Wilds several years before, and updated (information on the digitized charts added, and information about recent efforts to map the lunar polar regions provided by Anthony Mallama and Anthony Cook) on 2008 February 29.