Telescope mount

A mount is a device intended to perform the following tasks in practical astronomy:

In simple mounts to reduce the possibilities on the first page or the first and second point.

2.1 The Dobsonian mount

Equatorial Mounts

The equatorial mount, also called equatorial mount, a device for holding and movement of a telescope, in which, in contrast to other Montierungstypen, one of the axes is aligned exactly parallel to the Earth.

Advantage of the equatorial system

The oblique position of this axis, which means hours of right ascension axis or, indeed means greater mechanical effort, but has the advantage of being able to telescope tracking the apparent stellar orbits precisely.

The polar axis is inclined to the horizon at the angle of the latitude of the observation site. It shows exactly at Polaris. The second, on standing vertical axis points to the celestial equator and declination is called. Call the telescope and a counterweight is mounted in such a way that the overall system in mechanical equilibrium. The angle of rotation of the telescope about said second axis is the declination of the respective targeted Himmelskoordinate star.

The equatorial mount allows, caused by the earth's rotation, apparent movement of the stars in the telescopic observation by a corresponding counter movement to only one axis to compensate for the right ascension axis. One can thus every celestial object despite its apparent motion exactly in the visual field of the telescope stopped ( tracking). Montierungstypen other, for example, the Azimutalmontierung movements around at least two axes of which are required for this.

Equatorial Mounts can be manually tracked in the simplest case by a fine movement on the right ascension axis. To allow for astrophotography long exposure times of several minutes or even hours, it is sensible to use a motor drive. This requires a precise alignment of the mount, for example by means of a Polsuchers. Stepper motors with corresponding control make it possible to align the telescope at an observation object and to pursue this. Without such follow-up, there would be a line of evidence, and the objects would move out of the field. In case of insufficient alignment of the telescope at the celestial pole, there is a field rotation. Often located on both axes setting circles to locate the stars using coordinates.

Disadvantage of the equatorial system

The oblique position of the two main axes of the telescope can not be so easily adjusted, as it is usual, for example, from a tripod. Especially in Meridian problems may arise: When the Südmeridians exceeded the telescope must in some mounts will eventually become of the West in swirled the east facing position, because otherwise it abuts the mount and / or its height and thus the position of the eyepiece is too low. The interrupts an ongoing observation, the exposure of photographic images must be stopped.

On the north Meridian, in particular in the area of the pole, similar problems arise when a particular position must be achieved. To reach an object that only a few angular degrees is there in the vicinity of the pole away to another, may need to be already changed sides again. For telescopes with partial insight as Newtonian telescopes the insight by the swirling is often in a position no longer attainable; it must then be rotated into the pipe clamps in addition to the tube ( the telescope body ).

Equatorial Montierungsarten and their adjustment

For various observation instruments different variants of the equatorial mount were developed:

Some of these mounts is the focus of the telescope or Astro Count from the start at the intersection of the two axes ( fork mount, English Rahmenmontierung and Hufeisenmontierung ). All other mountings require compensation or counterweights, so that here also comes to lie in the axis of intersection of the center of gravity of all the moving parts.

For the correct orientation of German and other mounts sometimes a polar scope is used for smaller mobile instruments. Is not possible to install a Polsuchers, you can use the Scheiner - method for accurate alignment. It is observed whether the star track in the meridian of the instrument passes exactly horizontal.

For stationary instruments (at observatories or previous time services ) are used for precise orientation of the hour axis Miren also used.

Azimuth Mounts

Called azimuthal mounts, also alt- azimuth mount or altazimuth, have a vertical main axis ( vertical axis ) to which can rotate the entire system. The observation instrument itself can be pivoted about a horizontal axis between the horizon and the zenith. These mounts are mechanically simpler and viable. However, it must be accepted that the movements must be made about both axes with continuously variable speeds. In addition, the field of view of the scope rotates. That is, for astrophotography or gauges on the observation instrument must also be motor rotated. By using appropriate computer technology, however, these control problems can be solved today. The largest telescope systems have azimuthal mounts.

Also fork mounts are azimuthally aligned, but can be upgraded with a wedge or after and are then aligned equatorially.

There are also "Alt -Alt mounts " conceivable. The name is derived from old for height ( engl: altitude ). The major axis is horizontal. That is, the monitoring tool is pivoted about said axis both in the amount as well as about a second axis extending perpendicular to the first. This mount is more of theoretical interest.

The Dobsonian mount

The Dobsonian mount is a very simple form of azimuthal mount and was developed in the 1950s by John Dobson. The reason for its development was that should create a best possible mount for telescopes with large aperture. For the astrophotographic area this type of mount is suitable only with an equatorial platform. Short-term exposures to the moon and planets ( bright objects ) are possible with the help of a digital camera without tracking. The unfixed tube is attached to the eyepiece by the camera but so top-heavy that it must be stabilized by means of weights. The main advantage of this mount is in the low price and compact size. See also: Dobsonian telescope.

Equatorial platform

The equatorial platform is a plate on which an astronomical observation instrument with a simple azimuthal mount is constructed. The entire platform is supported so that they can compensate for the Earth's rotation for a limited time as a slow- moving cradle. Equatorial and azimuthal mounting platform can be so for a limited time to tracking the observation instrument. A field rotation does not occur here, so in conjunction with the equatorial platform a Dobsonian telescope for astrophotography is suitable.

Hexapod Mounts

The Hexapod Telescope Mount Mounts is as pure hardly in use. The movement of the observation instrument is obtained not by rotating about two axes, but by the change in length of six hydraulic cylinders. The demands on the precision of the variable-length elements is very high, compared to the mechanical effort for another mount choice.

The hexapodal mount has the advantage of having all six degrees of freedom, but is relatively limited in their range of motion. In conventional telescopes, the advantage of the degrees of freedom can not be used. It is therefore currently used among others by military telescopes for satellite tracking, and especially for the suspension of secondary mirrors in very large telescopes.

A prototype of a hexapod astronomical telescope with a primary mirror diameter of 150 cm was developed by Krupp in collaboration with the University of Bochum. From 1999 to 2004, it has been extensively tested in Bochum. In particular, the development of appropriate software proved to be complicated. In summer 2004 it was dismantled and brought to Chile Cerro Armazones, a telescope location of the Universidad Catolica del Norte, where it is to be used for astronomical observations by the Bochum Institute.