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Zenith stars (also "star on top", "overhead star", "latitude star") [7] are stars whose declination equals the latitude of the observers location, and hence at some time in the day or night pass culminate (pass) through the zenith. When at the zenith the right ascension of the star equals the local sidereal time at your location.
The observer would see a bright object appear in the northwest, which would move across the sky to a point almost overhead, where it disappears from view, in the space of three minutes. The following is a list of tools on a variety of platforms that may be used to predict the pass of an orbiting artificial satellite over a given point on Earth.
The GPS navigation message includes the difference between GPS time and UTC. As of January 2017, GPS time is 18 seconds ahead of UTC because of the leap second added to UTC on December 31, 2016. [156] Receivers subtract this offset from GPS time to calculate UTC and specific time zone values.
All-sky view of the 1998 Leonids shower. 156 meteors were captured in this 4-hour image.. In astronomy, the zenithal hourly rate (ZHR) of a meteor shower is the number of meteors a single observer would see in an hour of peak activity if the radiant was at the zenith, assuming the seeing conditions are perfect [1] (when and where stars with apparent magnitudes up to 6.5 are visible to the ...
A definition of a terrestrial time standard was adopted by the International Astronomical Union (IAU) in 1976 at its XVI General Assembly and later named Terrestrial Dynamical Time (TDT). It was the counterpart to Barycentric Dynamical Time (TDB), which was a time standard for Solar system ephemerides, to be based on a dynamical time scale ...
The current time is indicated by a golden ball or a picture of the sun at the end of a pointer. Local noon is usually at the top of the dial, and midnight at the bottom. Minute hands are rarely used. The Sun indicator or hand gives an approximate indication of both the Sun's azimuth and altitude. For azimuth (bearing from the north), the top of ...
In astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. the true horizon and north to an observer on Earth's surface). [1]
Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics ( classical mechanics ) to astronomical objects, such as stars and planets , to produce ephemeris data.