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The Carrington heliographic coordinate system, established by Richard C. Carrington in 1863, rotates with the Sun at a fixed rate based on the observed rotation of low-latitude sunspots. It rotates with a sidereal period of exactly 25.38 days, which corresponds to a mean synodic period of 27.2753 days.
At the equator, the solar rotation period is 24.47 days. This is called the sidereal rotation period, and should not be confused with the synodic rotation period of 26.24 days, which is the time for a fixed feature on the Sun to rotate to the same apparent position as viewed from Earth (the Earth's orbital rotation is in the same direction as the Sun's rotation).
The time when the Sun transits the observer's meridian depends on the geographic longitude. To find the Sun's position for a given location at a given time, one may therefore proceed in three steps as follows: [1] [2] calculate the Sun's position in the ecliptic coordinate system, convert to the equatorial coordinate system, and
This angle is made up of the angle due to latitude, combined with the angle due to the season, and the angle due to the time of day. These angles are set on the compass for a chosen time of day, the compass base is set up level using the spirit levels provided, and then the sights are aligned with the Sun at the specified time, so the image of ...
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. [1] [2] At solar noon, the zenith angle is at a minimum and is equal to latitude minus solar declination angle. This is the basis by which ancient mariners navigated the oceans. [3]
The solar azimuth angle is the azimuth (horizontal angle with respect to north) of the Sun's position. [ 1 ] [ 2 ] [ 3 ] This horizontal coordinate defines the Sun 's relative direction along the local horizon , whereas the solar zenith angle (or its complementary angle solar elevation ) defines the Sun's apparent altitude .
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On a prograde planet like the Earth, the sidereal day is shorter than the solar day. At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). More simply, 1→2 is a complete ...