Blue = solstitial colure
H = solstitial colure
Colure, in astronomy, is either of the two principal meridians of the celestial sphere. [1] The term is now rarely used and may be considered obsolete.
Colure, in astronomy, is either of the two principal meridians of the celestial sphere. [1] The term is now rarely used and may be considered obsolete.
The equinoctial colure is the meridian or great circle of the celestial sphere which passes through the celestial poles and the two equinoxes: [1] the first point of Aries and the first point of Libra. It is the great circle consisting of all points on the celestial sphere with Right Ascension equal to 0 hours or 12 hours (equivalent to RA 0° / 180°).
The equinoctial colure passes through the following constellations:
The solstitial colure is the meridian or great circle of the celestial sphere which passes through the poles and the two solstices: [1] the first point of Cancer and the first point of Capricorn. It is the great circle consisting of all points on the celestial sphere with Right Ascension equal to 6 hours or 18 hours (equivalent to RA 90° / 270°).
The solstitial colure passes through the following constellations:
A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
In astronomy, declination is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or south (negative) of the celestial equator, along the hour circle passing through the point in question.
Hipparchus was a Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry, but is most famous for his incidental discovery of the precession of the equinoxes. Hipparchus was born in Nicaea, Bithynia, and probably died on the island of Rhodes, Greece. He is known to have been a working astronomer between 162 and 127 BC.
Right ascension is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the point in question above the Earth. When paired with declination, these astronomical coordinates specify the location of a point on the celestial sphere in the equatorial coordinate system.
A solstice is the time when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 20–22 and December 20–22. In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes.
The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. Also within this zodiac belt appear the Moon and the brightest planets, along their orbital planes. The zodiac is divided along the ecliptic into 12 equal parts ("signs"), each occupying 30° of celestial longitude. These signs roughly correspond to the astronomical constellations with the following modern names: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.
The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects. It may be implemented in spherical or rectangular coordinates, both defined by an origin at the centre of Earth, a fundamental plane consisting of the projection of Earth's equator onto the celestial sphere, a primary direction towards the March equinox, and a right-handed convention.
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particular, axial precession can refer to the gradual shift in the orientation of Earth's axis of rotation in a cycle of approximately 26,000 years. This is similar to the precession of a spinning top, with the axis tracing out a pair of cones joined at their apices. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis—nutation and polar motion—are much smaller in magnitude.
An astrolabe is an astronomical instrument dating to ancient times. It serves as a star chart and physical model of visible heavenly bodies. Its various functions also make it an elaborate inclinometer and an analog calculation device capable of working out several kinds of problems in astronomy. In its simplest form it is a metal disc with a pattern of wires, cutouts, and perforations that allows a user to calculate astronomical positions precisely. It is able to measure the altitude above the horizon of a celestial body, day or night; it can be used to identify stars or planets, to determine local latitude given local time, to survey, or to triangulate. It was used in classical antiquity, the Islamic Golden Age, the European Middle Ages and the Age of Discovery for all these purposes.
Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials".
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest pole for the entire night on every night of the year. Others are called seasonal stars.
An armillary sphere is a model of objects in the sky, consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of celestial longitude and latitude and other astronomically important features, such as the ecliptic. As such, it differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations. It was invented separately, in ancient China possibly as early as the 4th century BC and ancient Greece during the 3rd century BC, with later uses in the Islamic world and Medieval Europe.
In observational astronomy, culmination is the passage of a celestial object across the observer's local meridian. These events were also known as meridian transits, used in timekeeping and navigation, and measured precisely using a transit telescope.
A pole star is a visible star that is approximately aligned with the axis of rotation of an astronomical body; that is, a star whose apparent position is close to one of the celestial poles. On Earth, a pole star would lie directly overhead when viewed from the North or the South Pole.
MUL.APIN is the conventional title given to a Babylonian compendium that deals with many diverse aspects of Babylonian astronomy and astrology. It is in the tradition of earlier star catalogues, the so-called Three Stars Each lists, but represents an expanded version based on more accurate observation, likely compiled around 1000 BCE. The text lists the names of 66 stars and constellations and further gives a number of indications, such as rising, setting and culmination dates, that help to map out the basic structure of the Babylonian star map.
The equator is a circle of latitude that divides a spheroid, such as Earth, into the Northern and Southern hemispheres. On Earth, the Equator is an imaginary line located at 0 degrees latitude, about 40,075 km (24,901 mi) in circumference, halfway between the North and South poles. The term can also be used for any other celestial body that is roughly spherical.
In astronomy, the hour circle is the great circle through a given object and the two celestial poles. Together with declination and distance, it determines the location of any celestial object. As such, it is a higher concept than the meridian as defined in astronomy, which takes account of the terrain and depth to the centre of Earth at a ground observer's location. The hour circles, specifically, are perfect circles perpendicular to the celestial equator. By contrast, the declination of an object viewed on the celestial sphere is the angle of that object to/from the celestial equator.
Constellation families are collections of constellations sharing some defining characteristic, such as proximity on the celestial sphere, common historical origin, or common mythological theme. In the Western tradition, most of the northern constellations stem from Ptolemy's list in the Almagest, and most of the far southern constellations were introduced by sailors and astronomers who traveled to the south in the 16th to 18th centuries. Separate traditions arose in India and China.
The northern celestial hemisphere, also called the Northern Sky, is the northern half of the celestial sphere; that is, it lies north of the celestial equator. This arbitrary sphere appears to rotate westward around a polar axis due to Earth's rotation.
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