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50. Moon Age Tables (1945)
- University Press of Colorado
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191 N o t e s o f M i d d l e A m e r i c a n A r c h a e o l o g y a n d E t h n o l o g y Carnegie Institution of Washington Division of Historical Research No. 50 February 15, 1945 moon Age Tables Lawrence Roys Following Goodman’s idea of giving Maya dates in tabular form, I present here two charts which link the age of the moon to a series of Maya dates. The first, and simpler of the two, needs little explanation beyond the legend. The dates shown in the chart are of conjunctions five lunar years apart. Intermediate conjunctions, or new-moon dates, can be determined by interpolation. It is suited to problems handled best with our decimal system, and demands the preliminary step of converting Maya vegesimal dates into decimal counting, conveniently defined as Maya Day dates by R. W. Willson (1924:17). This table is convenient for such problems as checking time intervals from the inscriptions against intervals between new moons, and for general use where it is easier to think in terms of our modern arithmetic. Of course, the moon age for any Maya date can be easily found with its aid. The second and more extensive table provides a quick method for obtaining the desired moon age for a given Maya date without converting it into Arabic notation. It is a series of Long Count dates, each accompanied by its moon age. They are close enough together to yield a date of known moon age conveniently near any given date of which the, moon age is unknown. Further columns are added so that the chart may be used for other general work. The detailed steps for finding the moon age for a given date, e.g. 9.5.6.14.3, are as follows: 1. Take from the 5-tun chart the Long Count date immediately preceding the given date, and transfer this with its moon age to a work sheet. E.g. 9.5.5.0.0, moon age 5 2/10. 2. Find the distance between these two dates by subtraction. E.g. 9.5.6.14.3 minus 95.5.0.0 equals 1.14.3. 3. Referring to the multiplication table at the side of the pages, select the highest multiple that does not exceed the remainder just found in Step 2. E.g. select 1.13.0 1/10 which is less than 1.14.3. 4. This highest multiple should be subtracted from the remainder found in Step 2. E.g. 1.14.3 minus 1.13.0 1/10 equals 1.2 9/10 (22 9/10 days). (This fourth step is a condensation of two arithmetical operations, and in effect gives us the distance that our given date lies beyond an intermediate date whose moon age is 5 2/10. With such a distance reduced to less than a month, it becomes hardly more than a matter of inspection finally to determine the moon age for our given date. The actual figure for the intermediate date does not appear in this solution as it has canceled itself out.) 5. To the remainder just obtained in Step 4 should be added the moon age from the 5-tun chart obtained in Step 1. E.g. 1.2 9/10 plus 5 2/10 equals 1.8 1/10 (28 1/10 days). This gives the unknown moon age desired for our given date. If this final answer exceeds 29 ½ days, it can be corrected by the simple expedient of subtracting 29 5/10 days. The computation on the work sheet appears as follows: lawrence royS 192 Given Date 9.5.6.14.3 1. 5-tun chart date 9.5.5.0.0 . . . of moon age 5 2/10 2. Remainder 1.14.3 3. Highest multiple 1.13.0 1/10 4. 2d remainder 1.2 9/10 (or 22.9 days) 5. Moon age from (1) 5 2/10 (or 5.2 days) 5. Desired moon age 1.8 1/10 (or 28.1 days) After a little practice, only the last five lines need be written down as the first simple subtraction can be solved by inspection. Hyphens are used here before the kin and the uinal so that tenths of days can be written decimally without causing confusion. This is after the manner of...