polar axis


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polar axis

1. The axis in an equatorial mounting that is parallel to the Earth's axis and hence points toward the celestial poles.
2. See poles.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

polar axis

[′pō·lər ′ak·səs]
(crystallography)
An axis of crystal symmetry which does not have a plane of symmetry perpendicular to it.
(mathematics)
The directed straight line relative to which the angle is measured for a representation of a point in the plane by polar coordinates.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
You then click on one of the surrounding stars several times as you turn the mount around its polar axis, for the software to determine the axis of rotation.
Initially I was concerned that the repeated assembly of the polar scope would upset its alignment with the polar axis. This proved to be a non-issue.
Since the mount's polar axis is aimed 35[degrees] above horizontal (Flagstaff's latitude), and the 960-pound polar shaft would be extremely difficult to remove at such an angle, Nye designed an I-beam support structure set at -35[degrees], to tilt the whole mounting at an unnatural angle.
The Moon rotates at a constant velocity around its polar axis (its day is of constant length), but because of its elliptical orbit around Earth, its orbital movement slows down when it is farthest from Earth and speeds up when closest in accordance with Kepler's Second Law of planetary motion.
It is touted as a "Z balanced" design because it has the telescope and the counterweights at opposite ends of the polar axis. Compared to a traditional German equatorial mount, the ZEQ25GT's center of gravity is closer to the middle of the equatorial head, leading to better inherent stability.
The gear on the polar axis is 18 1/2 inches in diameter with 584 teeth, while the declination gear is 15 inches with 480 teeth.
Typically the polar axis is fixed at the angle of a street elbow, usually 45[degrees].
The multi-star alignments also allow the electronics to calculate how far the polar axis is offset from the celestial pole, but it isn't easy to use this information to refine your polar alignment because there are no fine calibration marks on the mount's altitude and azimuth adjustments.
Since the scope's optical axis lies on an imaginary extension of the siderostat's polar axis, the mount has to be made for the latitude of the observing site.