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Celestial Coordinates
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Erstellt für das OAE
Unterschrift: Here we see how celestial coordinates map positions on the celestial sphere. The celestial sphere is an imaginary, hollow sphere that surrounds the Earth. Celestial objects appear to be attached to the inside of the celestial sphere, and the planets, Sun, and Moon appear to move slowly across it.
The celestial sphere has a spherical coordinate system similar to the latitude and longitude we see on the Earth. The celestial equator is the projection of the Earth's equator onto the celestial sphere while the north and south celestial poles are the projections of the Earth's north and south poles onto the celestial sphere.
Declination is similar to latitude on the Earth in that it marks the angle above and below the celestial equator. Declination is zero on the celestial equator, is positive to the north of the celestial equator and negative to the south of it. It is commonly measured in degrees and sometimes in radians.
Right Ascension is similar to longitude as it marks the angle around the celestial equator. As with longitude the zero point of right ascension (shown here as a dashed line) is a matter of choice. Traditionally the zero point of right ascension was the position of the Sun at the northern hemisphere vernal equinox (spring equinox) in March. It is positive and increases to the east, unlike longitude on Earth which is defined as east or west of the prime meridian. It is most commonly measured in hours, minutes and seconds or occasionally in degrees or radians.
The ecliptic marks the Sun's path across the celestial sphere when viewed from the Earth.
The Earth rotates within the celestial sphere. This leads to objects like stars or galaxies, which appear static on the celestial sphere, rising and setting when viewed from the Earth but remaining in the same position on the celestial sphere.
The Earth's axis precesses within the celestial sphere. This slowly moves the celestial equator and the celestial poles meaning that the traditional celestial coordinate system changes slowly over time meaning that stars and galaxies that do not move will have positions that change. Astronomers have used coordinate systems defined by the position of the celestial poles and equator at a fixed point in time. Now celestial positions are most commonly measured on a fixed coordinate system defined by the position of the celestial poles and equator on the 1st of January 2000.
Bild: Maria Cristina Fortuna/IAU OAE
Kategorien:
Astronomie mit bloßem Auge
, Beobachtende Astronomie
Lizenz: Creative Commons Namensnennung 4.0 International (CC BY 4.0) Creative Commons Namensnennung 4.0 International (CC BY 4.0) Symbole
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Antlia Constellation Map
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Unterschrift: The constellation Antlia along with its bright stars and surrounding constellations. Antlia is surrounded by (going clockwise from the top): Hydra, Pyxis, Vela and Centaurus.
Antlia is a southern constellation that is visible at some point in the year from the whole southern hemisphere as well as equatorial and some temperate regions of the northern hemisphere. The constellation is best viewed in the evenings in the northern hemisphere spring and southern hemisphere autumn.
The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
Link zur Quelle
Glossar-Begriffe:
Scheinbare Helligkeit , Himmelskoordinaten , Sternbild , Deklination , Rektaszension (RA)
Kategorien:
Astronomie mit bloßem Auge
Lizenz: Creative Commons Namensnennung 4.0 International (CC BY 4.0) Creative Commons Namensnennung 4.0 International (CC BY 4.0) Symbole
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Equuleus Constellation Map
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Unterschrift: The constellation Equuleus with its brighter stars and surrounding constellations. Equuleus is surrounded by (going clockwise from the top): Delphinus, Aquarius and Pegasus. It is a relatively small constellation with few bright stars.
Equuleus lies just north of the celestial equator and thus the whole constellation is visible at some point in the year to all but the most antarctic regions. Equuleus is best viewed in the evening in the early northern hemisphere autumn and early southern hemisphere spring.
The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
Link zur Quelle
Glossar-Begriffe:
Scheinbare Helligkeit , Himmelskoordinaten , Sternbild , Deklination , Rektaszension (RA) , Wassermann
Kategorien:
Astronomie mit bloßem Auge
Lizenz: Creative Commons Namensnennung 4.0 International (CC BY 4.0) Creative Commons Namensnennung 4.0 International (CC BY 4.0) Symbole
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Telescopium Constellation Map
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Unterschrift: The constellation Telescopium with its bright stars and surrounding constellations. Telescopium is surrounded by (going clockwise from the top): Corona Australis, Ara, Pavo, Indus, Microscopium and Sagittarius.
Telescopium is a southern constellation and thus the whole constellation is visible at some point in the year throughout the southern hemisphere. The whole constellation is also visible in equatorial and some temperate regions of the northern hemisphere. Telescopium is best viewed in the evening in the northern hemisphere summer and southern hemisphere winter.
The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
Link zur Quelle
Glossar-Begriffe:
Scheinbare Helligkeit , Himmelskoordinaten , Sternbild , Deklination , Rektaszension (RA) , Schütze
Kategorien:
Astronomie mit bloßem Auge
Lizenz: Creative Commons Namensnennung 4.0 International (CC BY 4.0) Creative Commons Namensnennung 4.0 International (CC BY 4.0) Symbole
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Volans Constellation Map
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Unterschrift: The constellation Volans with its bright stars and surrounding constellations. Volans is surrounded by (going clockwise from the top): Carina, Pictor, Dorado, Mensa and Chamaeleon.
Volans is a southern constellation and thus the whole constellation is visible at some point in year throughout the southern hemisphere. The whole constellation is also visible to a strip of the northern hemisphere near the equator. Volans is best viewed in the evening in the late northern hemisphere winter and late southern hemisphere summer.
The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Bild: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
Link zur Quelle
Glossar-Begriffe:
Scheinbare Helligkeit , Himmelskoordinaten , Sternbild , Deklination , Rektaszension (RA)
Kategorien:
Astronomie mit bloßem Auge
Lizenz: Creative Commons Namensnennung 4.0 International (CC BY 4.0) Creative Commons Namensnennung 4.0 International (CC BY 4.0) Symbole
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