Accuracy of medieval Chinese and Middle-Eastern timings of eclipses

Analysis of 111 Chinese timings of solar and lunar eclipses in the period AD 434–1280 and of 56 Middle-Eastern timings in AD 829–1020 reveals that their accuracy approached the limiting resolution of their clock systems. The Chinese accuracy improved progressively over the period of observation, with the standard deviation reducing from approximately 18 minutes round about AD 600 to 7 minutes circa AD 1200. The Middle-Eastern timings have a standard deviation of 5 minutes around AD 950.

The heliocentric path of the Moon

In his Astronomie populaire, Camille Flammarion points out that the heliocentric path of the Moon, which, according to him, has generally been represented as a sinuous curve, is actually concave everywhere towards the Sun. Flammarion’s observation is the starting point of this study which goes backwards in time, via often misinformed authors, to the mathematician who first established this counterintuitive property by means of a purely geometrical proof. The story also includes a heated debate between readers of a British periodical. Beginning in France at the end of the 19th century, the journey finishes in Scotland in the first half of the previous century.

On the chronology of the Anonymous Commentary to Ptolemy’s Tetrabiblos: Analysis of the astronomical evidence

In this paper, a proposal is made that the Anonymous Commentary to Ptolemy’s Tetrabiblos (Anon. in Ptol.) was composed not before 467 and not after 575 AD. In establishing the terminus post quem and the terminus ante quem, the Author relies on astronomical data provided by the Anonymous himself in his commentary to Ptolemy, Tetrabiblos (=Ptol. Tetr.) II.10 (p. 76, ll. 16-29 Wolf). In this passage, he reports that his master completely succeeded in interpreting the appearance of a celestial beam (δοκός) as a sign of a great loss of trunks, after which a naval battle took place where many ships were sunk; moreover, the master of the anonymous commentator predicted that the comet would remain visible until the end of Mercury’s retrogradation, and so it happened. As will be seen below, it is possible to crosscheck all this data to obtain a precise date of the comet’s appearance: 467 AD, 1 year before the naval battle of Cape Bon (468 AD). These years are also consistent with the dating that can be obtained from one of the horoscopes transmitted by the anonymous commentary (p. 98 Wolf), which corresponds to a birth that actually took place in Lower Egypt on 25 June 448 AD.

Three Gallo-Roman bronze disks with astral inscriptions

This article concerns three archaeologically recovered circular bronze objects found at Gallo-Roman (first century BC–fourth century AD) sites in France. Through comparisons with other more or less contemporary objects of known function, it is argued that one of these disks definitely, and another likely, belonged to gearwork devices for keeping track of simple chronological cycles, while the third belonged to a clepsydra of a type recognized only recently.