theAbysmal Calendar ~ Astronomical Facts

A few givens regarding calendar time.

theAbysmal Calendar is founded on astronomical observation as well as more familiar calendar features (weeks, months and so on). The US Naval Observatory provides a helpful glossary of time-related terms.

Time Definitions

[Note: abbreviations are theAbysmal’s]

second (s): The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. (International Bureau of Weights and Measures)

For those of us without any caesium 133 in the ground state handy, it is also equivalent to the average adult heartbeat at rest. Far less accurate but a little more poetic.

Day (D):  The unit of time, the second, was at one time considered to be the fraction 1/86 400 of the mean solar day. (International Bureau of Weights and Measures)

The solar day’s definition is left up to astronomers, as the duration varies during the course of the Earth’s orbit of the Sun. theAbysmal considers the Day to be 86,400 seconds long.

Lunation (L):  the synodic cycle of the Moon averages 29.530589 days (29 d 12 h 44 min 2.9 s) with a minimum of about 29.18 to a maximum of 29.93 days.

theAbysmal Calendar uses NASA’s Phases of the Moon catalogue to determine the length of any given Lunation, either as 29 or 30 Days.

Year (tropical) (Y): the period of time for the ecliptic longitude of the Sun to increase 360 degrees. Since the Sun’s ecliptic longitude is measure with respect to the equinox, the tropical year comprises a complete cycle of seasons…The mean tropical year is approximately 365 days, 5 hours, 48 minutes, 45 seconds.

Expressed as a fraction, the mean tropical year is 365.242 189 7 Days.

theAbysmal Time = Coodinated Universal Time (UTC) + 12 hours: If I’m not mistaken (I often am), this indicates midnight(ish) over 0 degrees longitude, which would begin the global day.

Earth’s Seasons:

Equinoxes: Either of the two points on the celestial sphere at which the ecliptic intersects the celestial equator.

equinox, autumnal: The descending node of the ecliptic on the celestial sphere. 2. The time which the apparent ecliptic longitude of the Sun is 180°.

equinox, vernal:  The ascending node of the ecliptic on the celestial equator. 2. The time at which the apparent ecliptic longitude of the Sun is 0°.

theAbysmal Calendar refers to the autumnal equinox as the Southward Equinox, as it occurs when the Sun appears over the Equator at noon as it heads towards the Southern Tropic (aka Tropic of Capricorn). The vernal equinox is therefore referred to as the Northward Equinox as the Sun moves towards the Northern Tropic (aka Tropic of Cancer). This nomenclature is intended to avoid confusion with those living in the Southern Hemisphere, as their autumn and spring are opposite of those in the Northern Hemisphere.

Solstices: either of the two points on the ecliptic at which the apparent longitude of the Sun is 90° or 270°; also the time at which the Sun is at either point.

southern solstice:  the solstice where the Sun appears over the Southern Tropic (aka Tropic of Capricorn) at noon.

northern solstice:  the solstice where the Sun appears over the Northern Tropic (aka Tropic of Cancer) at noon.

Aphelion: the point in an orbit that is the most distant from the Sun.

Perihelion: the point in an orbit that is nearest to the Sun.

theAbysmal Calendar uses USNO data to schedule these events.

 Planetary cycles

theAbysmal Calendar tracks the synodic periods of the planets. The inferior planets (Mercury, Venus) begin their cycle at inferior conjunction, the superior planets (Mars, Jupiter, Saturn, Uranus, Neptune) begin their cycle at conjunction.

Solar Cycle: The amount of magnetic flux that rises up to the Sun’s surface varies with time in a cycle called the solar cycle. This cycle lasts 11 years on average. This cycle is sometimes referred to as the sunspot cycle.

The dates of the beginning of any given Solar Cycle are difficult to define with precision, however NASA as well as other space observers assign dates. The current Solar Cycle 24 began January 8th 2008.

Start Times and Duration

theAbysmal Calendar begins each time period in darkness as much as is possible.

locally; midnight
globally; midnight over 0° longitude, equivalent to UTC + 12 hours
duration:  86,400 seconds

starts: New Moon
duration: 29.530589 Days

starts: Southern Solstice
duration: 365.242 189 7 Days

Inferior Planetary Cycle:
begins: Inferior Conjunction
Mercury; 115.88 Days
Venus; 583.92 Days

Superior Planetary Cycle:
begins: Conjunction
Mars; 779.96 Days
Jupiter; 398.88 Days
Saturn; 378.09 Days
Uranus; 369.66 Days
Neptune; 367.49 Days

Precession of the Equinoxes and the Constellations of the Zodiac
Precession of the Equinoxes
: … a Greek astronomer, Hipparchus of Nicea … proposed that the axis around which the heavens seemed to rotate shifted gradually, though very slowly.

Viewed from Earth, the Sun moves around the ecliptic, one full circuit each year. Twice a year, at equinox, day and night are equal and the Sun rises exactly in the east and sets exactly in the west. Ancient astronomers had no good clocks and could not tell when the day and night had the same length, but they could identify the equinox by the Sun rising exactly in the east and setting exactly in the west. At those times the Sun’s position is at one of the intersections between the ecliptic and the celestial equator.

Around the year 130 BC, Hipparchus compared ancient observations to his own and concluded that in the preceding 169 years those intersections had moved by 2 degrees.

theAbysmal  Calendar tracks the Precession of the Equinoxes through the use of the astronomical constellations of the Zodiac.

Zodiac: referring to the stars that form the background of the Ecliptic. This is no longer really part of theAbysmal Calendar due to its inordinately heavy western bias. I think a common starting point in the circle of constellations (or asterisms) might be possible. Currently the Sun passes into the boundary of Aries April 18th. Due to the precession of the equinoxes, this date will fall one day earlier every 71 years or so.

starts: when the Sun enters Aries (equivalent to April 18th).
Aries; 25 Days
Taurus; 39 Days
Gemini;  29 Days
Cancer; 21 Days
Leo; 37 Days
Virgo; 44 Days
Libra; 24 Days
Scorpio; 6 Days
Ophiuchus; 17 Days
Sagittarius; 35 Days
Capricorn; 27 Days
Aquarius; 23 Days
Pisces; 38 Days

theAbysmal Calendar
Perpetual 13-Month Calendar
Lunisolar Calendar
Calendar Symbolism

Chromatic Counter

Historical Eras

Astronomical Facts
Abbreviations & Notation
Arguments for Calendar Reform
theAbysmal Calendar for Download

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