Search results
Results From The WOW.Com Content Network
Historically setting circles have rivaled the telescopes optics as far as difficulty in construction. Making a set of setting circles required a lot of precision crafting on a dividing engine. Setting circles usually had a large diameter and when combined with a vernier scale could point a telescope to nearly an arc minute of accuracy.
The time is read off on the equatorial ring; in the example below, the center bar is twisted until a sunray passes through a small hole and falls on the horizontal equatorial ring. Traveller's sundial or universal ring dial, a portable version of astronomical rings, closed for carrying.
A large German equatorial mount on the Forststernwarte Jena 50cm Cassegrain reflector telescope. An equatorial mount is a mount for instruments that compensates for Earth's rotation by having one rotational axis, called polar axis, parallel to the Earth's axis of rotation. [1] [2] This type of mount is used for astronomical telescopes and cameras.
Equatorial (red) and horizontal (blue) celestial coordinates. A star 's spherical coordinates are often expressed as a pair, right ascension and declination , without a distance coordinate. The direction of sufficiently distant objects is the same for all observers, and it is convenient to specify this direction with the same coordinates for all.
The term transit theodolite, or transit for short, refers to a type of theodolite where the telescope is short enough to rotate in a full circle on its horizontal axis as well as around its vertical axis. It features a vertical circle which is graduated through the full 360 degrees and a telescope that could "flip over" ("transit the scope").
The metric system counterpart of the MOA is the milliradian (mrad or 'mil'), being equal to 1 ⁄ 1000 of the target range, laid out on a circle that has the observer as centre and the target range as radius. The number of milliradians on a full such circle therefore always is equal to 2 × π × 1000, regardless the target range. Therefore, 1 ...
The easiest way to understand the use of an equatorial ring is to imagine a ring placed vertically in the east-west plane at the Earth's equator. At the time of the equinoxes, the Sun will rise precisely in the east, move across the zenith, and set precisely in the west. Throughout the day, the bottom half of the ring will be in the shadow cast ...
Visualization of a celestial sphere. In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth.All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, which may be centered on Earth or the observer.