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Appendix III. Eclipses During the Reign of Emperor Yüan
i. HS 9: 8b says, In Yung-kuang II, "iii (the third month), on [the day] jen-hsü, the first day of the month, there was an eclipse of the sun." Han-chi 22: 6b repeats this statement. HS 27 Cb: 15a adds, "It was eight degrees in [the constellation] Lou."
Hoang equates this date with Mar. 28, 42 B.C.; Oppolzer calculates his solar eclipse no. 2777 for Mar. 27, 42 B.C. at 23th 45m Greenwich Civil Time (which was Mar. 28 at 7:00 a.m., local time at Ch'ang-an), and charts the path of totality as passing through Japan and Kamchatka. He calculates the sun at conjunction as in long. 4° = 4° R.A. The principal star of the constellation Lou, β Arietis, was then in 2° R.A.
In the 12 years between this and the preceding recorded eclipse, four solar eclipses were visible in China: Oct. 21, 53, Aug. 21, 50, Aug. 9, 49, and June 19, 47 B.C.
ii. HS 9: 9b says, In Yuan-Kuang IV, vi "on mou-yin, the last day of the month, there was an eclipse of the sun." Han-chi 22: 9b repeats the statement. HS 27 Cb: 15a adds, "It was 7 degrees in [the constellation] Chang."
Hoang equates this date with July 31, 40 B.C.; Oppolzer calculates his solar eclipse no. 2784 for that date and charts the path of totality as passing through the present northern Manchuria and Hondo, Japan. He calculates the sun as being in long. 124° = 127° R.A.; the first star in Chang, # Hydrae, was then in 121° R.A. There is thus a very close correspondence between the record and calculation. In the 2 years between this and the preceding recorded eclipse, no solar eclipses were visible in China.
iii. In Chien-chao V, vi, on jen-shen, the last day of the month, an eclipse is listed (9: 12b; Han-chi 23: 6b repeats this statement). HS 27 Cb: 15a adds, "It was partial, like a hook, then it set." Hoang gives this date as Aug. 23, 34 B.C., but there was no eclipse on that date.
In the eleven years from the last correctly recorded eclipse to the next correctly recorded one in 29 B.C., there were 25 solar eclipses, of which four were visible in China: 1
(1) The eclipse of July 20, 39 B.C. reached a magnitude (sun's diameter = 1.00) of only 0.07 at 2:43 p.m. local time at Ch'ang-an, so that it could easily be missed. (2) The eclipse of Jan. 14, 38 B.C. (2 days before a jen-shen day), reached only a magnitude of 0.02 at sunset at Ch'ang-an, so that it would be very likely missed. Visibility was better at points north and east. At lat. 40° and the long. of Ch'ang-an, this eclipse-reached a magnitude of 0.15. (3) The eclipse of Nov. 12, 36 B.C. (the day after a jen-wu day) reached a magnitude of 0.29 at Ch'ang-an at sunrise. (4) The eclipse of Nov. 1, 35 B.C. reached a magnitude of 0.66 when the sun set at Ch'ang-an. In view of the statement in the "Treatise" regarding the eclipse and its character, this must have been the eclipse concerned.
It occurred in IV, ix, on ting-ch'ou, the last day of the month. Since ting-ch'ou may be easily misread as jen-shen, the reliability of Hoang's calendar and of the HS record is confirmed. This eclipse must have been misdated before that chapter was written, for the "Annals" lists it among materials belonging in the wrong year.
It is noteworthy that during this period of a quarter century, seven out of the ten eclipses that might have been visible, if the weather permitted it, were missed. Evidently the court astronomers were not looking for solar eclipses, or else they could have seen at least some of these seven. This period was not one during which portents were overlooked; the misgovernment of Shih Hsien induced the annalists to record many portents. It seems as if the astronomers were satisfied with the calendar, and hence did not bother to look for solar eclipses.
1. Of the 9 partial eclipses, nos. 2789, 2797, 2798, 2807, and 2808 were located near the south pole. Nos. 2796, 2806, and 2809 were found plainly invisible by the use of Oppolzer's elements. The other one, no. 2799, was calculated from Neugebauer's elements and found invisible in China.Of those whose location Oppolzer charts, no. 2790 seemed possibly visible; calculation, however, showed that it was invisible in China.
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