STATION
, or Stationary, in Astronomy, the position or appearance of a planet in the same point of the zodiac, for several days. This happens from the observer being situated on the earth, which is far out of the centre of their orbits, by which they seem to proceed irregularly; being sometimes seen to go forwards, or from west to east, which is their natural direction; sometimes to go backwards, or from east to west, which is their retrogradation; and between these two states there must be an intermediate one, where the planet appears neither to go forwards nor backwards, but to stand still, and keep the same place in the heavens, which is called her Station, and the planet is then said to be Stationary.
Apollonius Pergæus has shewn how to find the Stationary point of a planet, according to the old theory of the planets, which supposes them to move in epicycles; which was followed by Ptolomy in his Almag. lib. 12, cap. 1, and others, till the time of Copernicus. Concerning this, see Regiomontanus in Epitome Almagesti, lib. 12, prop. 1; Copernicus's Revolutiones Cœlest. lib. 5, cap. 35 and 36; Kepler in Tabulis Rudolphinis, cap. 24; Riccioli's Almag. lib. 7, sect. 5, cap. 2: Harman in Miscellan. Berolinens, pa. 197. Dr. Halley, Mr. Facio, Mr. De Moivre, Dr. Keil, and others have treated on this subject. See also the articles Retrograde and Stationary in this Dictionary.
Station, in Practical Geometry &c, is a place pitched upon to make an observation, or take an angle, or such like, as in surveying, measuring heights-anddistances, levelling, &c.
An accessible height is taken from one Station; but an inaccessible height or distance is only to be taken by making two Stations, from two places whose distance asunder is known. In making maps of counties, provinces, &c, Stations are fixed upon certain eminencies &c of the country, and angles taken from thence to the several towns, villages, &c.—In surveying, the instrument is to be adjusted by the needle, or otherwise, to answer the points of the horizon at every Station; the distance from hence to the last Station is to be measured, and an angle is to be taken to the next Station; which process repeated includes the chief practice of | surveying.—In levelling, the instrument is rectified, or placed level at each Station, and observations made forwards and backwards.
There is a method of measuring distances at one Station, in the Philos. Trans. numb. 7, by means of a telescope. I have heard of another, by Mr. Ramsden; and have seen a third ingenious way by Mr. Green of Deptford, not yet published; this consists of a permanent scale of divisions, placed at any point whose distance is required; then the number of divisions seen through the telescope, gives the distance sought.
Station-Line, in Surveying, and Line of Station, in Perspective. See Line.
