Canon of the Season-Granting System, Part 2

Part of the Sources and Studies in the History of Mathematics and Physical Sciences book series (SHMP)

[This section sets out the elements of timekeeping; see the orientation, p. 82. The Centered Star (chung-hsing 中星) refers to whatever star is culminating (crossing the meridian) at a given moment. Most often it designates a star in one of the lunar lodges, since astronomers knew its distance from the determinative, and thus its equatorial location. Determining culminations is not part of generating the ephemeris, but in the Yuan laymen still widely used rules of thumb based on sighting a star crossing the meridian to tell the time of night.

The Centered Star in the planetary technique, step 7.1, is an arc, not directly related to a planet’s culmination or to the timekeeping techniques in this section. The purpose of each step is to
  1. 5.1.

    Tabulate declination and polar distance of ecliptic, and day and night lengths

  2. 5.2.

    Compute daily polar distance of ecliptic, using table

  3. 5.3.

    Compute length of day and night

  4. 5.4.

    Compute times of sunrise and sunset

  5. 5.5.

    Compute lengths of night watches and subdivisions

  6. 5.6.

    Compute times of night watches and subdivisions

  7. 5.7.

    Compute the nightly arc of stellar motion

  8. 5.8.

    Compute positions of stars that culminate at dusk, dawn, and each night watch

  9. 5.9.

    Compute day and night marks for any latitude]



Solar Eclipse Polar Distance Motion Part Summer Solstice Winter Solstice 
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© Springer Science+Business Media LLC 2009

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