| Diurnal Motion |
Article Index for Diurnal |
Website Links For Motion |
Information AboutDiurnal Motion |
| CATEGORIES ABOUT DIURNAL MOTION | |
| astrometry | |
| spherical astronomy | |
|
Direction of the motion in the Northern hemisphere:
Thus northern Circumpolar Star s move anti-clockwise around the North Star. At the North Pole, north, east and west are not applicable, the motion is simply left-right, or looking vertically upward, anti-clockwise around the Zenith . For the southern hemisphere, interchange north/south and left/right, and replace North Star by southern celestial pole. The circumpolar stars move clockwise around it. East/west are not interchanged. At the Equator both celestial poles are at the horizon and motion is anti-clockwise (i.e. to the left) around the North Star and clockwise (i.e to the right) around the southern celestial pole. All motion is from east to west, except for the two stationary points. The daily path of an object on the Celestial Sphere , including the possible part below the horizon, has a length proportional to the cosine of the Declination . Thus the speed of the diurnal motion of a celestial object is this cosine times 15 °/hr = 15'/min = 15"/s, i.e. (compare Angular Diameter ):
Diurnal motion can be seen in , which requires adjusting the Right Ascension only; a Telescope may have a motor to do that automatically (sidereal drive). SEE ALSO |
|
|