R - |
|
Reflector | A telescope in which the light is collected by means of a mirror. |
Resolution | The minimum detectable angle an optical system can detect. Because of diffraction, there is a limit |
| to the minimum angle, resolution. The larger the aperture, the better the resolution. |
Right Ascension: (RA) | The angular distance of a celestial object measured in hours, minutes, and seconds along the |
| Celestial Equator eastward from the Vernal Equinox. |
S - |
|
Schmidt Telescope | Rated the most important advance in optics in 200 years, the Schmidt telescope combines the best |
| features of the refractor and reflector for photographic purposes. It was invented in 1930 by |
| Bernhard Voldemar Schmidt |
Sidereal Rate | This is the angular speed at which the Earth is rotating. Telescope tracking motors drive the |
| telescope at this rate. The rate is 15 arc seconds per second or 15 degrees per hour. |
T - |
|
Terminator | The boundary line between the light and dark portion of the moon or a planet. |
U - |
|
Universe | The totality of astronomical things, events, relations and energies capable of being described |
| objectively. |
V - |
|
Variable Star | A star whose brightness varies over time due to either inherent properties of the star or something |
| eclipsing or obscuring the brightness of the star. |
W - |
|
Waning Moon | The period of the moon's cycle between full and new, when its illuminated portion is decreasing. |
Waxing Moon | The period of the moon's cycle between new and full, when its illuminated portion is increasing. |
Z - |
|
|
|
Zenith | The point on the Celestial Sphere directly above the observer. |
Zodiac | The zodiac is the portion of the Celestial Sphere that lies within 8 degrees on either side of the |
| Ecliptic. The apparent paths of the Sun, the Moon, and the planets, with the exception of some |
| portions of the path of Pluto, lie within this band. Twelve divisions, or signs, each 30 degrees in |
| width, comprise the zodiac. These signs coincided with the zodiacal constellations about 2,000 years |
| ago. Because of the Precession of the Earth's axis, the Vernal Equinox has moved westward by |
| about 30 degrees since that time; the signs have moved with it and thus no longer coincide with the |
| constellations. |
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