{{unreferenced, date=February 2014 Goto telescope

amateur astronomy Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers m ...

, "GoTo" refers to a type of

telescope mount A telescope mount is a mechanical structure which supports a telescope. Telescope mounts are designed to support the mass of the telescope and allow for accurate pointing of the instrument. Many sorts of mounts have been developed over the year ...

and related

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

that can automatically point a

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

astronomical object An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...

s that the user selects. Both axes of a GoTo mount are driven by a

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

and controlled by a computer. It may be either a

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

-based integrated controller or an external

personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...

. This differs from the single-axis semi-automated tracking of a traditional clock-drive

equatorial mount An equatorial mount is a mount for instruments that compensates for Earth's rotation by having one rotational axis, the polar axis, parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras. The ...

. The user can command the mount to point the telescope to the

celestial coordinates Astronomical coordinate systems are organized arrangements for specifying positions of satellites, planets, stars, galaxies, and other celestial objects relative to physical reference points available to a situated observer (e.g. the true hor ...

that the user inputs, or to objects in a pre-programmed database including ones from the

Messier catalogue The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only int ...

, the

New General Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and ...

, and even major

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

bodies (the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

, and

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

s). Like a standard

, equatorial GoTo mounts can track the

night sky The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include ...

by driving the

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired w ...

axis. Since both axes are computer controlled, GoTo technology also allows telescope manufacturers to add equatorial tracking to mechanically simpler

altazimuth mount An 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 bea ...

How a GoTo mount works

GoTo mounts are ''pre-aligned'' before use. When it is powered on, it may ask for the user's latitude, longitude, time, and date. It can also get this data from a

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

receiver connected to the telescope or built into the telescope mount itself, and the mount controller can have its own real time clock.

Alt-azimuth mounts

Alt-azimuth GoTo mounts need to be aligned on a known "alignment star", which the user will centre in the eyepiece. From the inputted time and location and the star's

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

and

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

the telescope mount will know its orientation to the entire sky and can then find any object. For accuracy purposes, a second alignment star, as far away as possible from the first and if possible close to the object to be observed, may be used. This is because the mount might not be level with the ground; this will cause the telescope to accurately point to objects close to the initial alignment star, but less accurately for an object on the other side of the sky. An additional reason for using two alignment stars is that the time and location information entered by the user may not be accurate. For example, a one-degree inaccuracy in the latitude or a 4-minute inaccuracy in the time may result in the telescope pointing a degree away from the user's target. When the user selects an object from the mount's database, the object's altitude and azimuth will be computed from its

and

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the ...

. Then, the mount will move the telescope to that altitude and azimuth and track the object so it remains in the field of view despite Earth's rotation. Moving to the location is called ''slewing''. When

astrophotography Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky. The first photograph of an astronomical object (the Moon) was taken in 1840, but it was no ...

is involved, a further motor has to be used to rotate the camera to match the field of view for long exposure photographs.

Equatorial mounts

For an equatorial GoTo telescope mount, the user must align the mount by hand with either the north celestial pole or the south celestial pole. Assuming the user is accurate in the alignment, the mount points the telescope to a bright star, asking the user to center it in the eyepiece. Since the star's correct right ascension and declination is already known, the distance from what the user considered to be the celestial pole and the actual pole can be roughly deduced. Using another alignment star can further improve the accuracy of the alignment. After alignment the telescope mount will then know its orientation with respect to the night sky, and can point to any right-ascension and declination coordinates. When the user selects an object to view, the mount's

looks up the object's right ascension and declination and slews (moves) to those coordinates. To track the object so that it stays in the eyepiece despite Earth's rotation, only the right-ascension axis is moved.

External links

Aligning an equatorial-mounted GoTo telescope in the northern hemisphere
Telescopes Astronomy software

How a GoTo mount works

Alt-azimuth mounts

Equatorial mounts

See also

External links