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The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur from September 21 to 24. At the equinox, the Sun as viewed from the equator rises due east and sets due west ...
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
Systematically observing the sunrise, people discovered that it occurs between two extreme locations at the horizon and eventually noted the midpoint between the two. Later it was realized that this happens on a day when the duration of the day and the night are practically equal and the word "equinox" comes from Latin aequus, meaning "equal", and nox, meaning "night".
Unlike the equinox, the solstice time is not easy to determine. The changes in solar declination become smaller as the Sun gets closer to its maximum/minimum declination. The days before and after the solstice, the declination speed is less than 30 arcseconds per day which is less than 1 ⁄ 60 of the angular size of the Sun, or the equivalent ...
The equinox arrives on Saturday, marking the start of the fall season for the Northern Hemisphere. Here's what to know about how we split up the year using the Earth's orbit. As the Earth travels ...
Observers within 63°26' of the Equator can view twilight twice each day on every date between the month of the autumnal equinox and the month of vernal equinox between astronomical dawn, nautical dawn, or civil dawn, and sunrise as well as between sunset and civil dusk, nautical dusk, or astronomical dusk, i.e., from September 1 to March 31 of ...
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.
In astronomy, an equinox is either of two places on the celestial sphere at which the ecliptic intersects the celestial equator. [1] [2] [3] Although there are two such intersections, the equinox associated with the Sun's ascending node is used as the conventional origin of celestial coordinate systems and referred to simply as "the equinox".