position angle


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position angle

(PA; p.a.)
1. The direction in the sky of one celestial body with respect to another, measured from 0° to 360° in an easterly direction from north. It is used, for example, to give the position of the fainter component of a visual binary with respect to the brighter component.
2. The angle at which the axis of a planet or star, or some other line on a celestial body, is inclined to the hour circle passing through the center of the body; it is measured eastwards from 0° to 360° from north.

Position Angle

 

an angle on the celestial sphere between a direction given at some point and the hour circle through this point; it is measured counterclockwise from 0° to 360° from the northern sector of the hour circle. Position angles are used to determine the relative position of the components of binary stars and multiple systems and the directions of the proper motions of stars. They are measured with a position micrometer.

position angle

[pə′zish·ən ′aŋ·gəl]
(astronomy)
The angle formed by the great circle running through two celestial objects and the hour circle running through one of the objects.
In measuring double stars, the angle formed between the great circle running through both components and the hour circle going through the primary measured from the north through the east from 0 to 360°.
(navigation)
That angle of the navigational triangle at the celestial body having the hour circle and the vertical circle at its sides. Also known as parallactic angle.
References in periodicals archive ?
In the same way, the position relationship between the inner raceway and each roller at the bottom of the bearing is obtained, and the number and position angle of rollers which contact with the inner raceway are obtained.
Definition of Head Position Angles. In the proposed sensing system, an accelerometer is attached to the forehead of the subject mounted with 3M(tm) Micropore(tm) Surgical Tape in the orientation shown in Figure 4(a), where x-axis points toward the head of the head, y-axis points to the right-hand side of the body, and z-axis points to the front of the head.
With a well calibrated reticle micrometer, we may expect measurements to average about [+ or -] 1 degree in the position angle and [+ or -] 2% in separation from the data listed in the WDS Catalog.
The obtained result shows that an increase in the difference of temperatures between the plant leaf and the environment by one degree (1[degrees]C) predetermines a 40% increase in plant leaf temperature change [DELTA]t regardless of plant leaf thickness [delta], leaf position angle [beta], duration of being in a certain position [tau] or oscillation frequency f.
The mean lateral component position angle and the SD were calculated for the series of radiographs of each hip (Fig.
Where R(z) is the flute radius at z, [phi] is the tool offset magnitude, [lambda] is the tool offset position angle, and [[psi].sub.i,j](z) is the angle measured backwards starting from the tip of the ith flute up to the portion of the cutting edge in the jth disk, and N is the number of the flutes of the tool.
"Air contact, heading three-five-zero, position angle two!" shouted aft lookout Operations Specialist 2nd Class David Beem.
The position on the curve is determined by the "position angle." Angles in Fig.
In the 16-inch at 229x it appears about 5' long, a 12:1 [Gottlieb 7:1] splinter in position angle 66[degrees] (east-northeast to west-southwest) with a very elongated core.
For observations of comets to be of scientific value the observer should concentrate on the following: estimates of the total visual magnitude of the comet (preferably made over the entire apparition to allow construction of a light curve), the diameter of the coma, the degree of condensation, estimates of the length and position angle of the tail, and detailed visual descriptions, sketches and photographs.
2013 May 7.15, appears slightly brighter than prev., coma diameter 5.5', DC=6/, slight hint of tail visible in position angle (p.a.) 280[degrees].
The International Occultation Timing Association (IOTA) undertakes a worldwide programme of video-recording lunar occultations of known and suspected double stars, to ascertain their duplicity, position angle, separation and difference in magnitude.