Text #260

Kronk. Cometography: A Catalog of Comets. Series: Cometography. Vol. 1
[pp. 19--21]

The oldest source of Information for this comet was the Han shu (100). It reports a “guest star” was observed by the Chinese “at the northeast of Kuan-So [α, β, γ, δ, ε, θ, ι, π, and ρ Coronae Borealis] moving in a southerly direction” on -68 August 20 (probably August 20.5 UT). On August 27 it “entered the T’ien-Shih Enclosure [Hercules, Serpens, Ophiuchus, and Aquila], with its rays pointing toward the southeast.” The Chinese said the object was white.

109P/-68 Q1 (Swift—Tuttle) Discovered: -68 August 20.5 (Δ =0.64 AU, γ=0.99 AU, Elong.=70°) Last seen: -68 August 27 (Δ =0.64 AU, γ=0.98 AU, Elong.=69°) Closest to the Earth: -68 August 23 (0.6247 AU)Calculated path: HER (Disc), CrB (Aug. 21), HER (Aug. 25), OPH (Sep. 1)

A. G. Pingré (1783) began a trend with this comet when he incorrectly included the object of -68 July 23 with the observations. Subsequently, Benjamin Peirce (1846) computed an orbit using the observations gathered by Pingré and determined that the comet passed perihelion in -68 July.Not everyone was convinced that the objects seen in -68 July and August were the same. Around the time Peirce was working on the orbit, Édouard C. Biot was constructing a catalog of novae seen since ancient times. One of the objects in his catalog was the “nova” of -68 July 23. Several years later, Adolf Berberich made the suggestion that the July object might have been a meteor train. H. H. Kritzinger (1908) was led to the comet of -68 during his investigation of the orbit of comet C/1858 L1 (Donati). He noted the similarity between the orbits of comet Donati and the comet of -68, although he did acknowledge a 47° difference in inclination. Kritzinger considered the possibility that the July object was not related to the August object. He then tried to link the August -68 observations with comet Donati, but concluded identity was not possible. The comet of -68 came up again during an investigation into the orbit of comet 109P/Swift-Tuttle in 1972. In a private communication, I. Hasegawa suggested to B. G. Marsden that the -68 August observations might represent this comet and gave the likely perihelion date as August 25. A paper published by Marsden in 1973 concludes that the August observations represented the “only really good candidate for [a previous apparition of] P/Swift-Tuttle,” while the July comet must be a separate comet. Marsden added that 17 revolutions of 109P/Swift-Tuttle probably occurred between this apparition and that of 1862. Hasegawa (1979) later revised the perihelion date to -68 August 26±1. After the recovery of 109P/Swift-Tuttle in 1992, the link with the August object of -68 was confirmed. Calculations by Graeme Waddington and Marsden an orbit with a perihelion date of -68 August 27.5. In a paper published in Icarus in 1993, Marsden, G. V. Williams, G. W. Kronk, and Waddington presented details of the observational history of Swift-Tuttle, including this apparition.

full Moon: August 4, September 3

Text #261

Yeomans. Comets

69 BC, August 20, China. A guest star was seen at the northeast of Corona Borealis moving in a southerly direction. On August 27 it entered the region near southern Hercules with its white tail pointing southeast.

Text #9719

Pankenier & Xu & Jiang. Archaeoastronomy in East Asia

1st year of the Dijie reign period of Emperor Xuan of the Han Dynasty, 6th month, day bingyin [3]; a guest star reappeared northeast of Guansuo, moving southward, until the 7th month, on the night of day guiyou [10], when it entered Tianshi, its rays of flame pointing southeast and its color was white.

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