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Solar longitude, commonly abbreviated as Ls, is the ecliptic longitude of the Sun, i.e. the position of the Sun on the celestial sphere along the ecliptic.It is also an effective measure of the position of the Earth (or any other Sun-orbiting body) in its orbit around the Sun, [1] usually taken as zero at the moment of the vernal equinox. [2]
At one date in the year, the Sun would be directly overhead at the North Pole, so its declination would be +90°. For the next few months, the subsolar point would move toward the South Pole at constant speed, crossing the circles of latitude at a constant rate, so that the solar declination would decrease linearly with time.
April 20, 2023 Solar Eclipse Parameters Parameter Value Eclipse Magnitude 1.01320 Eclipse Obscuration 1.02657 Gamma −0.39515 Sun Right Ascension 01h51m01.7s Sun Declination +11°24'54.1" Sun Semi-Diameter 15'55.4" Sun Equatorial Horizontal Parallax 08.8" Moon Right Ascension 01h51m43.2s Moon Declination +11°04'16.7" Moon Semi-Diameter 15'53.6"
U.S. Naval Observatory Sun or Moon Altitude/Azimuth Table ; The simple geometry of sun, moon, and star paths; Sun path calculation and visualization on Android; Sun path in augmented reality; Sun path by location and date; Sun positions, diagram and paths around the world by location and date; Seasonal and Hourly Sun Path Design Issue Tutorial
Year 4 of SC25 (Dec 2022 to Nov 2023) averaged 41% more spots per day than year 4 of SC24. Year 5 of SC25 (Dec 2023 to Nov 2024) averaged 71% more spots per day than year 5 of SC24. Year 6 of SC25 (1 Dec 2024 to 3 Jan 2025) is currently averaging 27% more spots per day than at the same point in year 6 of SC24.
On the date of the equinox, the center of the Sun spends a roughly equal amount of time above and below the horizon at every location on the Earth, so night and day [d] are about the same length. Sunrise and sunset can be defined in several ways, but a widespread definition is the time that the top limb of the Sun is level with the horizon. [ 28 ]
The Almanac specifies for each whole hour of the year the position on the Earth's surface (in declination and Greenwich hour angle) at which the Sun, Moon, planets, and First Point of Aries [clarification needed] is directly overhead. The positions of 57 selected stars are specified relative to the First Point of Aries.
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.