Another Look at Ptolemy's IVY Leaf

“Ptolemy's Ivy Leaf”, Journal for the history of astronomy , xv (1984), 32–34.

Other examples are illustrated in connection with the question of identifying the Greek “cissoid”, or “ivy-shaped curve”, in my Ancient tradition of geometric problems (Boston/Basel/Stuttgart, 1986), 246–63.

For the Greek text, see Heiberg's J. L. edition, Ptolemaei Syntaxis mathematica (2 parts, Leipzig, 1898–1903), II, 100–1. For alternative translation, see Toomer G. J. , Ptolemy's Almagest (New York/Berlin/Heidelberg/Tokyo, 1984), 368; and Manitius K. , Ptolemäus Handbuch der Astronomie (2 vols, Leipzig, 1912–13), ii, 48.

For the Greek text, see Eratosthenis Catasterismorum reliquiae , ed. by Robert C. , 2nd edn (Berlin, 1963), 98. The Latin poet Hyginus, who includes Eratosthenes among his sources, describes Coma in the same terms: “7 stars gathered in a triangle at the tail of Leo” (text supplied by Robert , loc. cit. ).

This anomaly about the magnitudes is noted by Peters C. H. F. Knobel E. B. , Ptolemy's Catalogue of stars (Washington, D.C., 1915), 103.

The data are tabulated by Peters , op. cit. (ref. 5), where γ, 7 and 23 Com are given the reference numbers 494, 495, 496. Relative to 100 a.d., the differences in longitude are unusually large among Ptolemy's stars: + 2°29′, +2°45′, + 3°25′. Compared with 130 b.c., however, these are reduced to −0°42′, −0°26′, +0°14′. The three stars of Coma also share a large error in latitude (−1°35′, −1°34′, −1°24′) that remains unexplained.

The thesis of such a dependence is urged by Peters and Knobel on the basis of their analysis of Ptolemy's data, op. cit. (ref. 5). It is also advocated by Grasshoff G. , The history of Ptolemy's Star catalogue (New York, etc., 1990), who provides an ample survey of prior views in this controversy.