vertical circle


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vertical circle,

in astronomy, the great circle on the celestial sphere that passes from the observer's zenith through a given celestial body. In the altazimuth coordinate systemaltazimuth coordinate system
or horizon coordinate system,
astronomical coordinate system in which the position of a body on the celestial sphere is described relative to an observer's celestial horizon and zenith.
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 the altitudealtitude,
vertical distance of an object above some datum plane, such as mean sea level or a reference point on the earth's surface. It is usually measured by the reduction in atmospheric pressure with height, as shown on a barometer or altimeter.
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 of a body is measured along its vertical circle.

vertical circle

A great circle on the celestial sphere that passes through an observer's zenith and cuts the horizon at right angles.

Vertical Circle

 

an astronomical instrument for determining by observation the zenith angles of heavenly bodies, which serve as material for calculating their declination, as well as the geographic coordinates of the place of observation. The optical tube of the instrument for sighting the heavenly body can rotate around a horizontal axis. An accurately divided circle placed on this same axis serves to measure the vertical angles. The entire instrument can be set in any vertical by rotating it around the vertical axis; how-ever, the vertical circle is usually used for observation in the meridian. Observations with the vertical circle are conducted mainly when compiling absolute catalogs of declinations of stars. The idea of the vertical circle was proposed in the 19th century by V. Ia. Struve, the founder of the Pulkovo Observatory. The first vertical circle was set up at Pulkovo in 1839. A photographic vertical circle with a largely automated observation process was built at the Pulkovo Observatory in 1962.


Vertical Circle

 

a large circle of the celestial sphere passing through the zenith and nadir of the place of observation and a given point on the celestial sphere. The vertical circle that passes through the north and south points coincides with the celestial meridian. The vertical circle that passes through the east and west points is called the prime vertical.

vertical circle

[′vərd·ə·kəl ′sər·kəl]
(astronomy)
A great circle of the celestial sphere, through the zenith and nadir of the celestial sphere; vertical circles are perpendicular to the horizon.

vertical circle

A graduated disk mounted on an instrument in such a manner that the plane of its graduated surface can be placed in a vertical plane.

vertical circle

vertical circle
A great circle of the celestial sphere passing through the celestial poles as well as the observer's zenith and nadir. Vertical circles are per-pendicular to the horizon. The prime vertical circle, or the prime vertical, passes through the east and west points of the horizon. The principal vertical circle passes through the north and south points of the horizon and coincides with the celestial meridian.
References in periodicals archive ?
1862) from Gent, Belgium, and Victor Moritz Goldschmidt (1888-1947) from Oslo designed an attachable vertical circle for converting a normal Fuess Model II for use by the theodolite method.
The justification and centering apparatus was placed in a movable third graduated circle that was mounted perpendicular to the vertical circle.
The axis of this new vertical circle v carries two mutually perpendicular circular segmental guiding arcs and sliders b1 and b2, divided and reading by verniers to 5[prime], which replace the ordinary adjusting segments.
Leiss (1925) criticized all of the theodolite goniometers described above because of their one-sided positioning of the vertical circle.
Leiss both tackled the problem by positioning the axis of the vertical circle in two strong bearing supports.
In almost all models the measuring area was limited because the carrier of the vertical circle could only be revolved between the positions of the collimator, on one side, and the telescope mount, on the other.
2) The vertical circle stands perpendicular to the horizontal circle and is revolvable about it.
3) The third circle has an axis that can be placed in any space, and its circle plane is at right angles to the vertical circle.
Troughton and Simms, this difficulty is largely overcome by reflecting the line of reference - which is the line bisecting the angle between the telescope and collimator in the ordinary single-circle goniometer and the adapted one just referred to - at right angles to its normal position by means of mirrors, so that on rotation of the vertical circle round the axis of the horizontal circle the axis of the vertical circle may be brought into coincidence with the line of reference in two positions on diametrically opposite sides of the centre, and still be free for somewhat further movement beyond 180 [degrees] of movement thus already afforded.

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