Syzygy in the twenty-eight equatorial lodges as calculated according to the Sifen li 四分曆 for 2020.

Résumé 0

The twenty-eight equatorial lodges as per the Sifen li (85 CE). The sun and moon progress counterclockwise through the ring of lodges (L01–L28), and, unbeknownst to the Sifen li’s authors, the ring of lodges is effectively turning in the same direction vis-à-vis the twenty-four qi (the winter solsticeQ22, establishment of springQ01, spring equinoxQ04, etc.), albeit very slowly, in what we call the precession of the equinoxes. The letter d represents equatorial lodge-width, where one du 度 equals the displacement of the mean sun through the stars in one day, for an annual “circuit” of 365¼ du in 365¼ days. Due to their interrelation, d can be read either “du” or “days” and thought of in terms of time or space. As per our result for procedure 13, the sun and moon are represented here in conjunction—i.e. the point of “syzygy,” at “new moon,” where the two bodies fall on the same line in a given reference plane (here, the equator)—at “DipperL08 16 du and 552 parts,” which is to say 16 and 552/940 du (equivalent to 16.35°, but as a measure of perimeter rather than angle) into [Southern] DipperL08 as counted from its ‘guide star’ (juxing 距星), φ Sagittarii. Note that the time/position of winter solstice and the other qi has since moved from where they are in this diagram, and that “DipperL08 16 du and 552 parts” is not a particularly accurate prediction for the right ascension of this particular syzygy