Lunar eclipse in the context of "Metonic cycle"

In astronomy, diurnal motion (from Latin diurnus 'daily', from Latin diēs 'day') is the apparent motion of celestial objects (e.g. the Sun and stars) around Earth, or more precisely around the two celestial poles, over the course of one day. It is caused by Earth's rotation around its axis, so almost every star appears to follow a circular arc path, called the diurnal circle, often depicted in star trail photography.

The time for one complete rotation is 23 hours, 56 minutes, and 4.09 seconds – one sidereal day. The first experimental demonstration of this motion was conducted by Léon Foucault. Because Earth orbits the Sun once a year, the sidereal time at any given place and time will gain about four minutes against local civil time, every 24 hours, until, after a year has passed, one additional sidereal "day" has elapsed compared to the number of solar days that have gone by.

An eclipse is an astronomical event which occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three celestial objects is known as a syzygy. An eclipse is the result of either an occultation (completely hidden) or a transit (partially hidden). A "deep eclipse" (or "deep occultation") is when a small astronomical object is behind a bigger one.

The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the Earth's shadow. However, it can also refer to such events beyond the Earth–Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host planet, or a moon passing into the shadow of another moon. A binary star system can also produce eclipses if the plane of the orbit of its constituent stars intersects the observer's position.

In astronomy, a syzygy (/ˈsɪzədʒi/ SIZ-ə-jee; from Ancient Greek συζυγία (suzugía) 'union, yoking', expressing the sense of σύν (syn- "together") and ζυγ- (zug- "a yoke")) is a roughly straight-line configuration of three or more celestial bodies in a gravitational system.

The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations.

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season in its new moon phase, when the Moon's orbital plane is closest to the plane of Earth's orbit. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured. Unlike a lunar eclipse, which may be viewed from anywhere on the night side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years.

If the Moon were in a perfectly circular orbit and in the same orbital plane as Earth, there would be total solar eclipses at every new moon. Instead, because the Moon's orbit is tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. Solar (and lunar) eclipses therefore happen only during eclipse seasons, resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total. Total eclipses are rarer because they require a more precise alignment between the centers of the Sun and Moon, and because the Moon's apparent size in the sky is sometimes too small to fully cover the Sun.

The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic longitudes of the Sun and Moon differ by 180°). This means that the lunar hemisphere facing Earth—the near side—is completely sunlit and appears as an approximately circular disk. The full moon occurs roughly once a month.

The time interval between a full moon and the next repetition of the same phase, a synodic month, averages about 29.53 days. Because of irregularities in the moon's orbit, the new and full moons may fall up to thirteen hours either side of their mean. If the calendar date is not locally determined through observation of the new moon at the beginning of the month there is the potential for a further twelve hours difference depending on the time zone. Potential discrepancies also arise from whether the calendar day is considered to begin in the evening or at midnight. It is normal for the full moon to fall on the fourteenth or the fifteenth of the month according to whether the start of the month is reckoned from the appearance of the new moon or from the conjunction.

A total lunar eclipse occurred at the Moon’s ascending node of orbit on Thursday, October 28, 2004, with an umbral magnitude of 1.3100. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A total lunar eclipse occurs when the Moon's near side entirely passes into the Earth's umbral shadow. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly two hours, while a total solar eclipse lasts only a few minutes at any given place, because the Moon's shadow is smaller. Occurring about 5.4 days before apogee (on November 2, 2004, at 13:10 UTC), the Moon's apparent diameter was smaller.

This lunar eclipse is the last of a tetrad, with four total lunar eclipses in series, the others being on May 16, 2003; November 9, 2004; and May 4, 2004.

A total lunar eclipse occurred at the Moon’s ascending node of orbit on Tuesday, April 15, 2014, with an umbral magnitude of 1.2918. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A total lunar eclipse occurs when the Moon's near side entirely passes into the Earth's umbral shadow. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly two hours, while a total solar eclipse lasts only a few minutes at any given place, because the Moon's shadow is smaller. The Moon's apparent diameter was near the average diameter because it occurred 6.9 days after apogee (on April 8, 2014, at 10:50 UTC) and 7.6 days before perigee (on April 22, 2014, at 20:20 UTC).

This lunar eclipse is the first of a tetrad, with four total lunar eclipses in series, the others being on October 8, 2014; April 4, 2015; and September 28, 2015.

An eclipse season is a period of roughly 1 month, occurring roughly every six months, when the orbits of the Earth, Sun, and Moon align such that solar and lunar eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's orbital plane (tilted five degrees to the Earth's orbital plane), just as Earth's weather seasons are the result of the axial parallelism of Earth's tilted axis as it orbits around the Sun. During the season, the "lunar nodes" – the line where the Moon's orbital plane intersects with the Earth's orbital plane – align with the Sun and Earth, such that a solar eclipse is formed during the new moon phase and a lunar eclipse is formed during the full moon phase.

Only two (or occasionally three) eclipse seasons occur during each year, and each season lasts about 35 days and repeats just short of six months (173 days) later, thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. During the eclipse season, the Moon is at a low ecliptic latitude (less than around 1.5° north or south), hence the Sun, Moon, and Earth become aligned straightly enough (in syzygy) for an eclipse to occur. Eclipse seasons should occur 38 times within a saros period (6,585.3 days).

Khaṇḍakhādyaka (meaning "edible bite; morsel of food") is a Sanskrit-language astronomical treatise written by Indian mathematician and astronomer Brahmagupta in 665 CE. The treatise contains eight chapters covering such topics as the longitudes of the planets, diurnal rotation, lunar and solar eclipses, risings and settings, the moon's crescent and conjunctions of the planets. The treatise also includes an appendix which in some versions has only one chapter, and in other has three.

The treatise was written as a response to Aryabhata's Ardharatrikapaksa.

Svarbhānu (Sanskrit: स्वर्भानु, lit. 'Splendour of Radiance') is an asura traditionally held responsible for solar eclipses and lunar eclipses in Vedic mythology. The name is also used as an attribute of the asuras Rahu and Ketu in Puranic mythology, who are also connected to the solar eclipse and the lunar eclipse.

In astronomy, a tetrad is a set of four total lunar eclipses within two consecutive years.

The frequency of tetrads varies by century with the frequency of total lunar eclipses. This repeating cycle is called a tetradia. See Eclipse cycle for more information.

A total lunar eclipse occurred at the Moon’s descending node of orbit on Friday, May 16, 2003, with an umbral magnitude of 1.1294. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A total lunar eclipse occurs when the Moon's near side entirely passes into the Earth's umbral shadow. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly two hours, while a total solar eclipse lasts only a few minutes at any given place, because the Moon's shadow is smaller. Occurring only about 15 hours after perigee (on May 15, 2003, at 11:40 UTC), the Moon's apparent diameter was larger.

This lunar eclipse marks the beginning of a tetrad, with four total lunar eclipses in series, the others being on November 9, 2003; May 4, 2004; and October 28, 2004. The previous series was in 1985 and 1986, starting with the May 1985 lunar eclipse. The next series was in 2014 and 2015, starting with the April 2014 lunar eclipse.

A total lunar eclipse occurred at the Moon’s ascending node of orbit on Sunday, November 9, 2003, with an umbral magnitude of 1.0197. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A total lunar eclipse occurs when the Moon's near side entirely passes into the Earth's umbral shadow. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly two hours, while a total solar eclipse lasts only a few minutes at any given place, because the Moon's shadow is smaller. Occurring about 1.2 days before apogee (on November 10, 2003, at 7:00 UTC), the Moon's apparent diameter was smaller.

This lunar eclipse is the second of a tetrad, with four total lunar eclipses in series, the others being on May 16, 2003; May 4, 2004; and October 28, 2004.

A total lunar eclipse occurred at the Moon’s descending node of orbit on Tuesday, May 4, 2004, with an umbral magnitude of 1.3035. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A total lunar eclipse occurs when the Moon's near side entirely passes into the Earth's umbral shadow. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly two hours, while a total solar eclipse lasts only a few minutes at any given place, because the Moon's shadow is smaller. Occurring about 1.2 days before perigee (on May 6, 2004, at 0:30 UTC), the Moon's apparent diameter was larger.

This lunar eclipse is the third of a tetrad, with four total lunar eclipses in series, the others being on May 16, 2003; November 9, 2004; and October 28, 2004.