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Derek Haselden - Astronomical Glossary
Category: Meteorology and astronomy > Astronomy
Date & country: 05/11/2007, UK
Words: 797


Camelopardalis
English name: The Giraffe. Genitive name: Camelopardalis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Camelopardalis
The constellation Camelopardalis. English name: The Giraffe. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cancer
English name: The Crab. Genitive name: Cancri. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cancri
The constellation Cancer. English name: The Crab. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Canes Venatici
English name: The Hunting Dogs. Genitive name: Canum Venaticorum. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Canis Major
English name: The Greater Dog. Genitive name: Canis Majoris. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Canis Majoris
The constellation Canis Major. English name: The Greater Dog. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Canis Minor
English name: The Lesser Dog. Genitive name: Canis Minoris. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Canis Minoris
The constellation Canis Minor. English name: The Lesser Dog. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Canum Venaticorum
The constellation Canes Venatici. English name: The Hunting Dogs. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Capricorni
The constellation Capricornus. English name: The Sea-Goat. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Capricornids
Meteor shower. Most active day is Jul.8. Bright, yellow-blue meteors.

Capricornus
English name: The Sea-Goat. Genitive name: Capricorni. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Captured rotation
Rotation of an object that spins at the same rate as that object takes to orbit another object. Sometimes referred to as synchronous rotation. The Moon is a good example of an object that has captured rotation.

Carbon stars
Red stars of spectral type 'R' and 'N' which have carbon-rich atmospheres.

Carina
English name: The Keel. Genitive name: Carinae. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Carinae
The constellation Carina. English name: The Keel. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Carme
Satellite of the planet Jupiter. See TABLE 7. JUPITER - SATELLITE DATA

Cassegrain reflector
A type of reflecting telescope where the secondary mirror is convex and the reflected light is then passed through a hole in the main or primary mirror. The advantage of this design is that it may be made more compact than a Newtonian reflector of equal focal ratio.

Cassiopeia
English name: Cassiopeia (Queen). Genitive name: Cassiopeiae. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cassiopeia (Queen)
The constellation Cassiopeia. Genitive name: Cassiopeiae. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cassiopeiae
The constellation Cassiopeia. English name: Cassiopeia (Queen). Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

CCD
Charge Coupled Device. An electronic device used in place of conventional photographic film. They consist of a silicon chip which is sensitive to light, the chip being divided up into picture elements (pixels). Light falling onto the chip builds up an electrical signal which is passed on to a processing computer in the form of digital data for later storage and processing. In some cases the signal from the chip is passed direct to a monitor for immediate display. CCD's are very sensitive to light, much more so than photographic film, therefore exposures can be much shorter. The downside is that they are smaller in area and often have less resolution than normal film.

Celestial sphere
An imaginary sphere that surrounds the Earth, the Earth being at the centre of that sphere.

Centauri
The constellation Centaurus. English name: The Centaur. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Centaurus
English name: The Centaur. Genitive name: Centauri. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Central meridian
The imaginary north-south line that bisects a planet. It is used as a reference for estimating the longitude of planetary features as it rotates.

Central meridian transit
The passage of a particular feature on a planet across the planet's central meridian.

Cephei
The constellation Cepheus. English name: Cepheus (King). Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cepheid
A short period variable star with very regular variations in magnitude. The name comes from the prototype star Delta Cephei. Cepheids are important astronomically because there is a clear link between their luminosity and their period of variation. Cepheids are also known to be highly luminous, giant stars than can be seen from great distances - distances can then be calculated by sheer observation alone.

Cepheus
English name: Cepheus (King). Genitive name: Cephei. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cepheus (King)
The constellation Cepheus. Genitive name: Cephei. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Ceres
One of the `minor planets` of our solar system. Discovered by Piazzi on 1 Jan 1801. Diameter in km: 940. More data in TABLE 13. THE MINOR PLANETS

Ceti
The constellation Cetus. English name: The Whale. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cetus
English name: The Whale. Genitive name: Ceti. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Chaldene
Satellite of the planet Jupiter. See TABLE 7. JUPITER - SATELLITE DATA

Chamaeleon
English name: The Chamaeleon. Genitive name: Chamaeleontis. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Chamaeleontis
The constellation Chamaeleon. English name: The Chamaeleon. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Charon
Satellite of the (ex-)planet Pluto. See TABLE 11. PLUTO - SATELLITE DATA

Chromatic aberration
A defect present in all single lenses because different wavelengths of light come to a focus at different distances from the lens. This defect will show up as a false colour fringe around a star for example. The defect is corrected by using multiple lens arrangements using different types of glass.

Chromosphere
The part of the Sun's atmosphere that lies above the photosphere of the Sun.

Churyumov-Gerasimenko
A comet in our solar system with an orbital period of 6.61years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Circe
One of the `minor planets` of our solar system. Discovered by Chacornac on 6 Apr 1855. Diameter in km: 112. More data in TABLE 13. THE MINOR PLANETS

Circini
The constellation Circinus. English name: The Compasses. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Circinus
English name: The Compasses. Genitive name: Circini. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Circumpolar star
A star that never sets as seen from a particular location on Earth. For example, the stars of the Great Bear (Ursa Major) never set as seen from England.

Clark
A comet in our solar system with an orbital period of 5.51years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Collimation
The act of aligning the optical components of an instrument such as a telescope so that the instrument performs correctly.

Columba
English name: The Dove. Genitive name: Columbae. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Columbae
The constellation Columba. English name: The Dove. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Coma (cometary)
The cloud of gas and dust that makes up the head of a comet, the nucleus is at the centre.

Coma (optical)
An optical defect where objects close to the edge of a field of view appear to be flared or fanned out.

Coma Berenices
English name: Berenice's Hair. Genitive name: Comae Berenices. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Comae Berenices
The constellation Coma Berenices. English name: Berenice's Hair. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Comas Sola
A comet in our solar system with an orbital period of 8.94years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Conjunction
An instant when two celestial objects appear to lie very close together or in a line as seen from a particular viewpoint.

Conjunction, Inferior
A conjunction when one of the inferior planets (Mercury or Venus) appears to lie very close to the Sun, or in line with the Sun, as seen from Earth, but with the planet between Earth and the Sun. Obviously, a superior planet (Mars, Jupiter, Saturn, Uranus, Neptune or Pluto) cannot be at inferior conjunction!

Conjunction, Superior
A conjunction when one of the inferior planets (Mercury or Venus) appears to lie very close to the Sun, or in line with the Sun, as seen from Earth, but with the planet on the far side of the Sun.

Constellation
An area of the celestial sphere bounded by internationally decreed lines of Right Ascension and Declination. The whole celestial sphere is divided up into a total of 88 areas of varying size, each with its own name. The smallest is Crux (The Southern Cross) and the largest is Hydra (The Watersnake). The most common concept of a constellation is generally the pattern of stars (usually the brightest ones) that make up a familiar figure or pattern. But, strictly speaking, a constellation actually refers to an area of sky rather than the pattern. Without exception, a constellation's area exceeds the area of the pattern that gave that area its name.

Cordelia
Satellite of the planet Uranus. See TABLE 9. URANUS - SATELLITE DATA

Corona
The tenuous, outermost part of the Sun's atmosphere. It is visible to the naked-eye, but only at the time of a total solar eclipse or with the use of specialised instruments.

Corona Australis
English name: The Southern Crown. Genitive name: Coronae Australis. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Corona Borealis
English name: The Northern Crown. Genitive name: Coronae Borealis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Coronae Australis
The constellation Corona Australis. English name: The Southern Crown. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Coronae Borealis
The constellation Corona Borealis. English name: The Northern Crown. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Coronagraph
An instrument that allows study of the Sun's inner corona at times of non-eclipse.

Corvi
The constellation Corvus. English name: The Crow. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Corvus
English name: The Crow. Genitive name: Corvi. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cosmic rays
High velocity particles reaching Earth from outer space. The heavier cosmic ray particles are broken up when they enter Earth's upper atmosphere.

Cosmogony
The study of the origin and evolution of the universe.

Cosmology
The study of the universe considered as a whole.

Counterglow
The English name for the skyglow opposite the Sun, very difficult to observe, caused by very thinly spread interplanetary material. Usually known by its German name, the Gegenschein.

Crater
English name: The Cup. Genitive name: Crateris. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Crateris
The constellation Crater. English name: The Cup. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cressida
Satellite of the planet Uranus. See TABLE 9. URANUS - SATELLITE DATA

Crommelin
A comet in our solar system with an orbital period of 27.4years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Crucis
The constellation Crux. English name: The Cross. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Crux
English name: The Cross. Genitive name: Crucis. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Culmination
The maximum altitude that a celestial object attains above the horizon.

Cygni
The constellation Cygnus. English name: The Swan. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Cygnus
English name: The Swan. Genitive name: Cygni. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

D'Arrest
A comet in our solar system with an orbital period of 6.51years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Daniel
A comet in our solar system with an orbital period of 7.06years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Daphne
One of the `minor planets` of our solar system. Discovered by Goldschmidt on 22 May 1856. Diameter in km: 204. More data in TABLE 13. THE MINOR PLANETS

Dawes limit
The maximum practical limit for the resolving power of a telescope. It is 4.56 / d, where d is the aperture in the instrument in inches. For example, the Dawes limit of a of a four inch telescope is 1.1 seconds of arc. A twelve inch instrument would have a Dawes limit of 0.4 seconds of arc. In other words, the Dawes limit is the theoretical point at which the telescope is able to separate two objects that distance apart. In practice this is seldom achieved.

Day, sidereal
The interval between two successive meridian passages (or culminations) of the same star. A sidereal day is equal to 23 hours, 56 minutes and 4.091 seconds. This is the true rotational period of the Earth.

Day, solar
The mean interval between successive meridian passages of the Sun. It is equal to 24 hours, 3 minutes and 56.55 seconds. The solar day is slightly longer than the sidereal day because the Sun seems to moves eastward against the stars, on average at roughly one degree per day.

de Vico-Swift
A comet in our solar system with an orbital period of 7.32years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Declination
The angular distance of a celestial object north or south of the celestial equator. It corresponds to latitude on Earth.

Deep-Sky
The part of space that lies beyond the Solar System. Star clusters, galaxies and nebulae are frequently termed as 'Deep-sky objects'.

Degree (Deg)
Symbol ┬░, 1/360th of a circle.

Deimos
Satellite of the planet Mars. See TABLE 6. MARS - SATELLITE DATA

Delphini
The constellation Delphinus. English name: The Dolphin. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Delphinus
English name: The Dolphin. Genitive name: Delphini. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

delta Aquarids
Meteor shower. Most active day is Jul.29. 2 radiants, rich shower, but faint meteors.

Denning-Fujikawa
A comet in our solar system with an orbital period of 9.01years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Density
The mass of an object per unit of its volume. Density is usually expressed as a numerical ratio to that of water which has a density of 1. An object denser than water would have a figure of greater than 1, and vice-versa.

Desdemona
Satellite of the planet Uranus. See TABLE 9. URANUS - SATELLITE DATA

Despina
Satellite of the planet Neptune. See TABLE 10. NEPTUNE - SATELLITE DATA

Dichotomy
The instant when an object is exactly half lit as seen from Earth. It is usually applied to the Moon or an inferior planet.