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The solar zenith angle is the zenith angle of the sun, i.e., the angle between the sun’s rays and the vertical direction.It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane.
Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction. Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the Earth. [1]
In astronomy, the altitude in the horizontal coordinate system and the zenith angle are complementary angles, with the horizon perpendicular to the zenith. The astronomical meridian is also determined by the zenith, and is defined as a circle on the celestial sphere that passes through the zenith, nadir, and the celestial poles.
The Earth's axial tilt is currently around 23.4°, and therefore so are the latitudes of the tropical circles, marking the boundary of the tropics: specifically, ±23°26′09.7″ (or 23.43603°). The northern one is called the Tropic of Cancer , and the southern is the Tropic of Capricorn .
Sunrise seen over the Atlantic Ocean through cirrus clouds on the Jersey Shore at Spring Lake, New Jersey, U.S. Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning, [1] at the start of the Sun path. The term can also refer to the entire process of the solar disk crossing the horizon.
The Sun's altitude remains within half a degree of the minimum of about 5 degrees for about 45 minutes either side of this time. When it rotates on its own axis, it sometimes moves closer to the Sun. During this period of Earth's rotation from May to July, Earth tilts at an angle of 23.5 degrees above its own axis in its orbit.
A slow motion of Earth's axis, precession, causes a slow, continuous turning of the coordinate system westward about the poles of the ecliptic, completing one circuit in about 26,000 years. Superimposed on this is a smaller motion of the ecliptic, and a small oscillation of the Earth's axis, nutation. [3] [4]
The plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator. In the cycle of Earth's seasons, the equatorial plane runs through the Sun twice a year: on the equinoxes in March and September. To a person on Earth, the Sun appears to travel along the equator (or along the celestial equator) at ...