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13 Cards in this Set
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the time it takes for a star in the sky to come back to the same place in the sky. |
sidereal day the earth rotates 360°. A sidereal day is 23 hours 56 minutes and 4.09 seconds long.
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sidereal year |
the time it takes for the sun to return to the same position with respect to the stars |
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the time it takes the sun to successively pass the meridian (astronomical noon) |
synodic or solar day |
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Because a tropical year is 365.242 mean solar days long,In an attempt to keep the Vernal Equinox very near March 21st,was introduced. |
Leap Year |
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the plane in which the earth orbits the sun. |
The ecliptic (The Zodiac is the twelve constellations that contain the ecliptic.) |
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Calculate meridional altitude |
altitude of celestial equator + declination of star (If the meridional altitude is above 90° one must subtract the number from 180° as altitude is only defined up to 90°. That is an altitude of 100° is really 80°) |
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It is idealized to be free from geographical effects a flat plane tangent to the earth's surface where the observer is standing |
The horizon= an observer can only see half of the celestial sphere at any given moment. |
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the other point is straight up |
zenith. |
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he coordinate defining directions parallel to the horizonfrom 0 to 360° starting with north = 0° and increasing towards the east. |
Azimuth |
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below the horizon isat altitude -90° |
nadir |
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they are always above the horizon |
circumpolar stars. |
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always below the horizon |
never rise stars |
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diagrams |
selestial sphere and horizon diagram |
