A true equinox would indicate 12 hours of both day and night. You must be logged in to reply to this topic. May peace be with you . These events are referred to as Equinoxes. I employed sin(angle*2) in the (poorly named) linearize(angle) code below to convert ecliptic longitudes to a function which crosses zero at each quadrant. The solstices and equinoxes are defined by Earth's position in its orbit relative to the Sun. National Weather Service But the axial tilt doesn't change too much in a given year, that's why the equinoxes and solstices fall in approximately the same dates. The source that everybody on the internet seems to use for the times of equinoxes is the US Naval Observatorys almanac (cited by 0. also that the day-of-week will not be correct when the date is in the Julian calendar (earlier than 1582-Oct-15). There are different expressions for each solstice or equinox, and different expressions for the year ranges -1000 to 1000 vs. 1000 to 3000. Viewing 2 posts - 1 through 2 (of 2 total), https://in-the-sky.org/news.php?id=20170922_07_100#exact_time, http://aa.usno.navy.mil/data/docs/EarthSeasons.php, https://astronomy.stackexchange.com/questions/10901/how-did-meeus-calculate-equinox-and-solstice-dates, This topic has 1 reply, 2 voices, and was last updated. Hooke's law is a principle of physics that states that the force needed to extend or compress a spring by some distance is proportional to that distance. Subscribe to Developer Insider for top news, trends & analysis, The Top Task Management Software for Developers, Online Courses to Learn Video Game Development. How did Meeus calculate equinox and solstice dates? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Are there accurate equinox and solstice predictions for the distant past? The solstice is determined by the Earth's tilt on its axis, not anything to do with the shape of its orbit: the solstice is the point when the poles come closest to pointing toward or away from the sun. On the day of the solstice or equinox, document the sun's direction (use the shadow of a vertical pole and your compass) and altitude (see below) throughout the day.
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