Reference frames

12 entries

• Cross-Quarter DaysConceptGaelicModern PaganModernCEvidence grade C of five, A strongest, E weakest: Insider writing from after a break in transmission

  Three defensible answers to when a cross-quarter day falls: the fixed calendar date, the solar-longitude midpoint, and the temporal midpoint of the season.

• Eastward Transmission of Hellenistic Astral MaterialConceptTang ChinaHellenistic

  Alexandrian astral material reached Tang China through Indian and Iranian intermediaries, by the same routes and the same translations that carried it west.

• Greek Loanwords in Sanskrit AstrologyConceptHellenisticModern

  Sanskrit horoscopic vocabulary carries Greek technical terms, and what that does and does not establish about how the two traditions met.

• Heliacal RisingsConceptHellenicRomanModernAEvidence grade A of five, A strongest, E weakest: Contemporary insider document, or a dated object

  Before calendars were reliable, the year was told by which stars were visible at dawn. The mechanism, the texts that use it, and why the dates drift.

• House DivisionConceptHellenisticIslamicateMedieval LatinRenaissance and early modernModern

  Seven house systems divide seven different objects into twelve, which is why a chart tool that offers all seven never agrees with itself.

• Precession of the EquinoxesConceptBabylonianHellenisticMedieval LatinModern

  The slow westward slide of the equinox against the stars: the rate, who first measured it, and why it separates the seasonal frame from the stellar one.

• Solstices and EquinoxesConceptModernGermanicGaelicAEvidence grade A of five, A strongest, E weakest: Contemporary insider document, or a dated object

  Four instants, not four dates. What they are, why the calendar date moves between years, and what pre-Christian Europe is recorded as having marked.

• The anglesConceptHellenisticMedieval LatinModern

  The four points where the ecliptic crosses the horizon and the meridian, how fast they move, and the latitudes at which they stop existing.

• The Astronomical Bureau and the Calendar CaseConceptMing and Qing ChinaHan ChinaRenaissance and early modern

  Calendar-making as a prerogative of state, the bureau that did it, and the prosecution of 1664 to 1669 that ended in a shadow measurement.

• The Chinese Lunisolar CalendarConceptHan ChinaMing and Qing ChinaModern

  Months set by conjunction, a solar year cut twenty-four ways, the leap-month rule, and the change from equal time to equal solar longitude.

• The Yavanajātaka and its DatingPrimary textHellenisticModern

  A Sanskrit astrological text long dated to the second and third centuries CE on readings its manuscripts do not contain, and the correction that followed.

• Three Reference FramesConceptHellenisticModern

  The tropical zodiac, the sidereal zodiac and the IAU constellation boundaries divide the sky for three different purposes, and answer three questions.