Eridanus Constellation Map

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图注： The constellation Eridanus with its bright stars and surrounding constellations. Eridanus is surrounded by (going clockwise from the top): Taurus, Cetus, Fornax, Phoenix, Tucana, Hydrus, Horologium, Caelum, Lepus and Orion. Eridanus is a large constellation that spans a wide range in declination. A small portion of the constellation is in the northern hemisphere with the southern-most point lying at a declination of almost -60°. As it spans the celestial equator, parts of the constellation are visible to the whole Earth at some point in the year. The whole constellation can be observed from northern and southern equatorial regions, southern temperate regions and most of Antarctica. Eridanus is best viewed in the evening in the northern hemisphere winter and 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.
来源： Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
来源链接

词汇表: 视星等 , 天球坐标 , 星座 , 赤纬 , 赤经（RA） , 金牛座 , 猎户座
分类： 肉眼天文学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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Total Solar Eclipse

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为 OAE 制作

图注： This not to scale diagram shows what happens during a total solar eclipse. The Moon orbits the Earth, but its orbit is slightly tilted with respect to the Earth’s orbit around the Sun. During the new moon lunar phase, the Moon lies between the Earth and the Sun, but due to the Moon’s tilted orbit around the Earth, the Moon normally lies above or below the Sun at this point. However twice a year the Moon’s orbit lines up in such a way that the Moon can lie in a direct line between the Earth and Sun. During this time a solar eclipse can occur. The Moon is about 400 times smaller than the Sun, but is 400 times closer to the Earth than the Sun. Hence the Sun and Moon have approximately the same angular size when viewed from the Earth. This means that it is possible for the Moon to completely cover the Sun when viewed from Earth. This is known as a total solar eclipse. Here we see a schematic of such and eclipse. The Moon casts a shadow on the Earth known as the umbra. This is a roughly circular shadow a few hundred kilometres across. Any region within the umbra will see the Moon completely cover the Sun and thus will experience a total solar eclipse. Outside of the umbra there are regions where the Moon will cover part of the Sun. This partial shadow is known as the penumbra. Regions in the penumbra will experience a partial solar eclipse. An eclipse is a dynamic event with the Moon moving in its orbit and the Earth rotating. Hence the umbra and penumbra move across the Earth’s surface. The path the umbra takes across the Earth is known as the path of totality. Let’s consider one particular region that lies in the path of totality. Except in rare cases where an eclipse begins at sunrise, a region that experiences totality will first see the Moon cover part of the Sun and gradually move across Sun until it is totally covered. From outside the Earth this would appear as the penumbra moving over this particular region followed by the umbra moving over this region. Once the Moon moves so that it no longer completely covers the Sun, totality ends and the umbra moves away from this particular region. The Moon will continue to uncover the Sun until (unless the Sun sets before the end of the eclipse) the Sun is completely uncovered. From outside the Earth this would appear as the umbra moving away from our particular region and the edge of the penumbra approaching and eventually passing over the region. Outside of the path or totality there is a much broader region that will lie in the penumbra but will be missed by the umbra. Such regions will not experience a total solar eclipse during this event, only a partial solar eclipse.
来源： Aneta Margraf/IAU OAE

词汇表: 月相 , 月球 , 新月 , 日偏食 , 半影 , 日食 , 太阳 , 日全食 , 本影
分类： 肉眼天文学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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Canes Venatici Constellation Map

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图注： The constellation Canes Venatici with its brighter stars and surrounding constellations. Canes Venatici is surrounded by (going clockwise from the top): Ursa Major, Coma Berenices and Boötes. Canes Venatici is a northern constellation and thus the whole constellation is visible at some point in the year from the whole of the northern hemisphere. The whole of the constellation is also visible from equatorial regions of the southern hemisphere with parts of it visible from temperate southern regions. The constellation is best viewed in the northern hemisphere late spring and southern hemisphere late autumn. The famous spiral galaxy commonly known as the Whirlpool Galaxy (M51) lies in Canes Venatici and is marked here with a red ellipse. Other notable spiral galaxies in the cluster include M63, M94, M106 and NGC 4631. All are marked here with red ellipses. The globular cluster M3 is marked here with a yellow circle with a plus symbol superimposed on it. 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.
来源： Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
来源链接

词汇表: 视星等 , 天球坐标 , 星座 , 赤纬 , 球状星团 , 赤经（RA） , 漩涡星系
分类： 肉眼天文学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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Hercules Constellation Map

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图注： The constellation Hercules with its bright stars and surrounding constellations. Hercules is surrounded by (going clockwise from the top): Draco, Boötes, Corona Borealis, Ophiuchus, Aquila, Sagitta, Vulpecula and Lyra. Hercules is a large, northern constellation that covers a big range in declination. The whole constellation is visible at some point in the year in the whole northern hemisphere and in equatorial regions of the southern hemisphere. Parts of the constellation can be viewed from temperate and almost all antarctic regions of the southern hemisphere. Hercules is best viewed in the northern hemisphere summer and southern hemisphere winter. The globular clusters M13 and M92 lie in Hercules and are marked here with yellow circles with plus signs superimposed on them. 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.
来源： Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
来源链接

词汇表: 视星等 , 天球坐标 , 星座 , 赤纬 , 球状星团 , 赤经（RA）
分类： 肉眼天文学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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Hydrus Constellation Map

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图注： The constellation Hydrus with its bright stars and surrounding constellations. Hydrus is surrounded by (going clockwise from the top): Eridanus, Phoenix, Tucana, Octans, Mensa, Dorado, Reticulum and Horologium. Hydrus is a southern constellation and thus the whole constellation is visible in the southern hemisphere at some point in the year. As it lies close to the celestial south pole, only a small part of the northern hemisphere near the equator can see the whole of Hydrus, with other northern equatorial regions able to see parts of the constellation. Hydrus is best viewed in the evenings in the northern hemisphere winter and southern hemisphere summer. This diagram maps an area around the south celestial pole. Here lines of constant right ascension converge. The right ascension values of these lines are marked on the x-axis above and below the diagram. The solid circle around the pole marks a line of -80° declination with the larger, incomplete circle to the right marking -70° declination. 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.
来源： Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
来源链接

词汇表: 视星等 , 天球坐标 , 星座 , 赤纬 , 赤经（RA）
分类： 肉眼天文学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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