HorizonMost commonly, the horizon is the border between the surface of a celestial body and its sky when viewed from the perspective of an observer on or above the surface of the celestial body. This concept is further refined as: The true or geometric horizon, which an observer would see if there was no alteration from refraction or from obstruction by intervening objects. The geometric horizon assumes a spherical earth.Fundamental plane (spherical coordinates)The fundamental plane in a spherical coordinate system is a plane of reference that divides the sphere into two hemispheres. The geocentric latitude of a point is then the angle between the fundamental plane and the line joining the point to the centre of the sphere. For a geographic coordinate system of the Earth, the fundamental plane is the Equator.
Celestial sphereIn 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. If centered on the observer, half of the sphere would resemble a hemispherical screen over the observing location.
AzimuthAn azimuth (; from Arabic: اَلسُّمُوت, romanized: as-sumūt, lit.'the directions') is the horizontalangle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system.
Great circleIn mathematics, a great circle or orthodrome is the circularintersection of a sphere and a diametral plane, which is a planepassing through the sphere's center point. DiscussionAny arc of a great circle is a geodesic of the sphere, so that great circles in spherical geometry are the natural analog of straight lines in Euclidean space. For any pair of distinct non-antipodalpoints on the sphere, there is a unique great circle passing through both.
SphereA sphere (from Ancient Greek (sphaîra)'ball') is a surface analogous to the circle, a curve. In solid geometry, a sphere is the set of points that are all at the same distance r from a given point in three-dimensional space. That given point is the center of the sphere, and the distance r is the sphere's radius. The earliest known mentions of spheres appear in the work of the ancient Greek mathematicians. The sphere is a fundamental surface in many fields of mathematics.
Spherical coordinate systemIn mathematics, a spherical coordinate system specifies a given point in three-dimensional space by using a distance and two angles as its three coordinates. These are the radial distance, r, along the line connecting the point to a fixed point called the origin; the polar angle, θ, between this radial line and a given polar axis; and the azimuthal angle, φ, which is the angle of rotation of the radial line around the polar axis.
FITSFlexible Image Transport System (FITS) is an open standard defining a digital file format used for storage, transmission and processing of data: formatted as multi-dimensional arrays (for example a 2D image), or tables. FITS is the most commonly used digital file format in astronomy. The FITS standard was designed specifically for astronomical data, and includes provisions such as describing photometric and spatial calibration information, together with image origin metadata.
Astronomical coordinate systemsIn astronomy, coordinate systems are used for specifying positions of celestial objects (satellites, planets, stars, galaxies, etc.) relative to a given reference frame, based on physical reference points available to a situated observer (e.g. the true horizon and north to an observer on Earth's surface).
SkyThe sky is an unobstructed view upward from the surface of the Earth. It includes the atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from outer space. In the field of astronomy, the sky is also called the celestial sphere. This is an abstract sphere, concentric to the Earth, on which the Sun, Moon, planets, and stars appear to be drifting.
Altazimuth mountAn altazimuth mount or alt-azimuth mount is a simple two-axis mount for supporting and rotating an instrument about two perpendicular axes – one vertical and the other horizontal. Rotation about the vertical axis varies the azimuth (compass bearing) of the pointing direction of the instrument. Rotation about the horizontal axis varies the altitude angle (angle of elevation) of the pointing direction.
TelescopeA telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally, it was an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects – an optical telescope. Nowadays, the word "telescope" is defined as a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.*As an Amazon Associate I earn from qualifying purchases.