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The Islamic calendar is a purely lunar calendar and has a year, whose start drifts through the seasons and so is not a solar calendar. The Maya Tzolkin calendar, which follows a 260-day cycle, has no year, therefore it is not a solar calendar. Also, any calendar synchronized only to the synodic period of Venus would not be solar.
The equation above neglects the influence of atmospheric refraction (which lifts the solar disc — i.e. makes the solar disc appear higher in the sky — by approximately 0.6° when it is on the horizon) and the non-zero angle subtended by the solar disc — i.e. the apparent diameter of the sun — (about 0.5°). The times of the rising and ...
Erasmus Reinhold used Copernicus' theory to compute the Prutenic Tables in 1551, and gave a tropical year length of 365 solar days, 5 hours, 55 minutes, 58 seconds (365.24720 days), based on the length of a sidereal year and the presumed rate of precession. This was actually less accurate than the earlier value of the Alfonsine Tables.
As at Dec 6, 2024, solar cycle 25 is averaging 39% more spots per day than solar cycle 24 at the same point in the cycle (Dec 6, 2013). Year 1 of SC25 (Dec 2019 to Nov 2020) averaged 101% more spots per day than year 1 of SC24. Year 2 of SC25 (Dec 2020 to Nov 2021) averaged 7% more spots per day than year 2 of SC24.
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 ...
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For example, a satellite in Sun-synchronous orbit might ascend across the equator twelve times a day, each time at approximately 15:00 mean local time. Sun-synchronous orbit from a top view of the ecliptic plane with local solar time (LST) zones for reference and a descending node of 10:30. The LST zones show how the local time beneath the ...
The widely used solar aspect is a cycle of leap days in a 400-year cycle designed to keep the duration of the year aligned with the solar year. [37] There is a lunar aspect which approximates the position of the moon during the year, and is used in the calculation of the date of Easter. [38]