Alt-azimuth mount or alt-azimuth mount
has vertical and horizontal axes of rotation, allowing you to rotate the telescope in height (“alt” from the English altitude) and azimuth and direct it to the desired point on the celestial sphere. To track space objects, moving along celestial sphere due to daily rotation Earth, the telescope must be rotated simultaneously around both axes at different variable speeds.
Mounts of this type are compact, lightweight and convenient for long trips and balconies, but have severe limitations in astrophotography. Due to the rotation of the field of view at long shutter speeds, it is difficult to use them for deep-sky photography (there are quite complex techniques shooting not suitable for a beginning astrophotographer). Nevertheless, with such a mount it is possible to take photographs of the Moon and planets, since their photography requires short shutter speeds, where field rotation is not a hindrance.
There are also automated mounts of this type, the use of which will allow you to avoid constant movement of the telescope along 2 axes and automatically point at objects. Such systems usually have a fork or semi-fork design.
The Dobsonian mount is also an alt-azimuth mount with all the attendant pros and cons.
Equatorial (parallax) mount- a device for mounting a telescope (or other astronomical instrument) so that one of the planes of its rotation is perpendicular earth's axis(and, accordingly, parallel to the celestial equator).
Due to the rotation of the Earth, over time, the observed extraterrestrial objects shift and “run away” from the field of view, which causes inconvenience during observations, and during astro photography it is a critical limitation for the shutter speed. The equatorial mount is designed to compensate for rotation globe by rotating the telescope along one axis in the plane of the celestial equator. It is enough to place a mechanism on this axis (parallel to the Earth's) that would rotate the telescope one revolution in 24 hours in the direction opposite to the rotation of our planet. Objects observed through such a telescope do not “run away” from the field of view, and the possibilities of astro photography are significantly expanded.
Compared to an alt-azimuth mount for rotation compensation
One motor is sufficient for ground control, which reduces guidance errors. Also, in such a mount there is no rotation of the field of view and it is theoretically possible to take exposures of any duration (the only limitation is the accuracy of the mechanism for compensating the Earth’s rotation).
There are also negative aspects to the equatorial mount. Due to the presence of counterweights in the system, the weight of the structure is significantly higher than that of alt-azimuth mounts. The mount also has significantly protruding moving parts, which makes it difficult to install in a confined space (for example, on a balcony). When setting up the mount, it takes more time, since it is necessary to accurately align the axes of rotation in accordance with the latitude of the area.
Equatorial mounts can be mechanical, with a drive to compensate for the rotation of the Earth, as well as fully automated with computer control.
General rules for choosing a mount:
If you have already decided on a telescope, now you need to understand which mount to choose. First of all, you need to remember that the mounts that come with the telescope are usually quite weak and selected to the limit of their capabilities. If you do not have the opportunity to buy a mount separately, then you need to determine the type and buy the most massive and heavy mount, preferably with a clock drive.
If you are planning astrophotography of objects deep space, then you should buy an equatorial mount of at least EQ5 class (preferably HEQ5, EQ6), always with a clock drive. For planet photography solar system Any mount will do, but again a guiding mechanism is highly desirable.
Equatorial or azimuthal?
It is impossible to say unequivocally that one or another type of mount is certainly better than others. Everyone has their pros and cons, otherwise there would be no alternatives. Let's take a closer look at the advantages and disadvantages of mounts of the two most popular types.
Altazimuth
These also include Dobsonian ones. This type is actively gaining popularity, and if previously azimuth mounts were typical only for the cheapest small telescopes, they are now used for the most high-tech models with large apertures.
Advantages of an altazimuth mount
A simple and stable mounting system that does not require counterweights on the axes and does not have significant masses far from the center of gravity, leading to vibrations and increasing the load on the tripod. In a typical case, one bearing horizontally and two vertically are sufficient.
Simple and intuitive for beginners.
More transportable than most equatorial ones, especially for apertures greater than 200 mm, and often quicker to prepare for observations.
Easy to build yourself.
More affordable, especially with large apertures.
Disadvantages of an altazimuth mount
It is impossible to drive an object with a motor along only one axis. For long-term guidance, a dual-motor computer-controlled system or a special equatorial platform is required. Moreover, even a dual-engine system cannot guide an object as it passes exactly through the zenith (“Dobsonian hole”).
Lack of constant orientation of the field of view relative to celestial coordinates makes it difficult to find faint objects using the “star jump” method.
If there are coordinate circles in azimuth and altitude, their use to search for objects requires a preliminary recalculation of coordinates, and this must be performed with a minimum delay, preferably on a computer in real time.
Rotating the field of view limits photography to short exposures (unless an expensive field derotator is used). Guiding at long exposures can be very tricky due to the unintuitive relationship between the image and the drift correction knobs.
Equatorial mounts
These mounts are installed according to the celestial coordinate system. They have been the main type of mount for amateur and professional telescopes for over a hundred years. There are quite a few of their designs: “German”, “English yoke”, “fork”, etc.
Advantages of equatorial mounts
You can use a clock drive on the right ascension axis for long-term tracking of a celestial object.
Most designs of equatorial mounts (except for the “yoke”) can be aimed at any point in the sky and guide the object.
The absence of field rotation makes it possible to engage in long-exposure astrophotography and intuitive correction when guiding, and also makes it a little easier to navigate during planetary observations.
The technique of searching for faint objects by drifting from a noticeable star in right ascension is applicable, including on telescopes without a clock drive.
To find objects invisible in the finder, coordinate circles can be used in right ascension and declination.
Disadvantages of equatorial mounts
A good equatorial mount is usually heavy and bulky. It is less portable than altazimuth; transportation often requires disassembling it into several parts.
The German equatorial mount uses heavy counterweights located on a long rod to balance the telescope. In the dark, it’s easy to accidentally stumble upon them and throw off the telescope’s aiming. It also happens that the pipe touches the tripod if it is aimed at the zenith, and it is necessary to “shift” it around its axis.
The removed load creates additional source vibration if the mount is not rigid enough. Fork mount brackets can sag under the weight of the pipe and cause tracking and pointing errors, as well as low-frequency vibrations.
Good equatorial mounts usually have four bearings and tend to be more expensive than comparable altazimuth mounts (though you can make them yourself, too).
To accurately track an object, precise aiming of the mount to the celestial pole is necessary.
Less intuitive for beginners, although with experience the time spent searching for an object becomes less than with altazimuth.
None of these shortcomings is a reason to refuse to use this or that type of mount in amateur practice. For purely visual observations, especially for beginners, we can recommend an altazimuth mount. And for photography with long exposures - equatorial. An azimuth mount can also be recommended for large apertures, but an equatorial “split ring” mount will also work for them. Computer equipment partially mitigates the differences in mount types, although it cannot completely eliminate them.
→ Telescope mountA mount is one of the most important components of the design of an optical telescope, on which the optical tube is mounted, and with the help of which the telescope can be directed towards the observed area of the sky. Any mount consists of a base, rotation axes (located mutually perpendicular), drives and a reference system for rotation angles. There are two main types of mounts: equatorial and azimuth (horizontal) mounts.
As a result of the Earth's rotation, celestial objects are constantly moving out of the telescope's field of view, forcing the observer to compensate given rotation using a mount. An equatorial mount includes two axes: the first is directed towards the celestial pole (polar axis), and the second lies in the equatorial plane (declination axis). To compensate for the daily rotation of the Earth, the observer must rotate the telescope with constant speed around one polar axis.
There are several types of equatorial mounts. In the English mount, the polar axis rests on two columns, and the declination axis bearing supports the telescope itself. In the German mount, the polar axis ends with a housing that carries the declination axis (suitable for long, lightweight refractor tubes). In the American mount, the polar axis ends with a fork that carries the declination axis (used for large telescopes).
The equatorial mount by its design is more complex system, as a result of which a telescope with such a mount will be much more expensive than a telescope with an azimuth mount. 
An azimuth mount includes two axes: a vertical, supporting pipe and used to rotate the telescope in height, and a horizontal one, used to rotate the telescope in azimuth. In the case of using a telescope with an azimuth mount, it will be much more difficult to compensate for the daily rotation of the globe, since in in this case you need to continuously rotate the telescope around two axes at different speeds.
A subtype of the alt-alt mount is the alt-alt mount, in which the two axes are perpendicular to each other. An azimuth mount is simpler, lighter and more compact than an equatorial mount, plus it is noticeably cheaper. An alt-azimuth mount is ideal for amateur astronomical observations, as well as observations of terrestrial objects. 
This mount is a type of alt-azimuth mount, which is a platform attached by an axis to a rotating alt-azimuth fork. At the ends of the racks there are special passes into which the declination semi-axes fit.
Azimuth mount
Azimuth Dobsonian mount.
Azimuth mount(altazimuth mount) - a telescope mount that has vertical and horizontal axes of rotation, allowing you to rotate the telescope in azimuth and height and direct it to the desired point on the celestial sphere. To track an object moving due to visible diurnal movement celestial sphere, the telescope must be rotated simultaneously around both axes at variable speeds. Azimuth mounts are used in radio telescopes. In professional optical telescopes, such a mount was first used in the USSR for the BTA.
see also
Wikimedia Foundation. 2010.
- Rodriguez, Evaristo
- Visual C++ 2005 Express Edition
See what “Azimuth mount” is in other dictionaries:
Azimuth mount- A telescope mount that has vertical and horizontal axes of rotation, allowing you to rotate the telescope in azimuth and height and direct it to the desired point in the celestial sphere. To track a star moving due to visible... ...
AZIMUTHAL MOUNTING- azimuth tripod, installation for a telescope with a vertical. and the horizontal axis of rotation. Used for astronomical purposes. tools, photos cameras for observing satellites, radio telescopes, large optical telescopes. telescopes, etc... Big Encyclopedic Polytechnic Dictionary
azimuth mount for amateur telescope- Mounting of an amateur telescope, in which the telescope can rotate around vertical axis to change the azimuth and around the horizontal axis to change the zenith distance. [GOST R 50701 94] Optics topics, optical instruments And… … Technical Translator's Guide
Alt-azimuth mount- Amateur telescope on an alt-azimuth mount. A... Wikipedia
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Telescope mount- Equatorial mount German type for an amateur telescope ... Wikipedia
Telescope mount- the part of the Telescope on which its optical tube is mounted. M. t. allows you to direct it to the observed area of the sky, ensures the stability of its installation in the working position, and the convenience of making observations various types. Basic... ... Great Soviet Encyclopedia
Dobsonian mount- Wooden Dobson mount with amateur telescope... Wikipedia
Equatorial mount- Equatorial mount a device for installing a telescope (or other astronomical instrument) so that one of the planes of its rotation is perpendicular to the earth’s axis (and, accordingly, parallel to the celestial equator).... ... Wikipedia
Dobson, John- John Dobson in 2002 John Dobson (born September 14, 1915) is a renowned American amateur astronomer. Inventor of the telescope mount of the same name, which is in great demand among amateur astronomers. Also famous for his efforts... Wikipedia
Alt-azimuth mount
Amateur telescope on an alt-azimuth mount.
Alt-azimuth mount(azimuth mount) - a telescope mount that has vertical and horizontal axes of rotation, allowing you to rotate the telescope in height ( "alto" from English altitude) and azimuth and direct it to the desired point on the celestial sphere. To track space objects moving across the celestial sphere due to the daily rotation of the Earth, the telescope must be rotated simultaneously around both axes at different variable speeds. An even more complex control principle is incorporated into alt-azimuth mounts designed for astro photography. To control them, it is necessary to ensure uneven alternating motion along two coordinates with an error not exceeding tenths of the diameter of the star image, and in addition to compensate for the rotation of observation objects in the focal plane. To summarize: an optical telescope on an altazimuth mount must be controlled in three coordinates: azimuth, zenith distance and parallactic angle.
In older scientific telescopes, built before the advent of modern computerized control systems, as well as in amateur telescopes, an equatorial mount is preferable, in which only 1 axis needs to be rotated at a constant speed. However, relative to the alt-azimuth mount, the equatorial mount for amateur telescopes has greater weight, size, price and a more complex design. An alt-azimuth mount is poorly suited for amateur astro photography and is more suitable for observing ground-based objects.
On the other hand, an alt-azimuth mount is used in modern large telescopes, since the vertical arrangement of one of the axes can significantly reduce and simplify the nature of the system’s deformation under the influence of gravity, which is of fundamental importance when the telescope has a significant mass.
In professional optical telescopes, such a mount was first used in the USSR for the BTA. The world's largest telescope (2009), the Keck telescope, and the Grand Canary Telescope also use this type of mount.
Due to the enormous weight of parabolic antennas, azimuth mounts are used in radio telescopes.
see also
Notes
Links
- (Russian) Alt-azimuth mount in astroslover.
- (Russian) Types of mounts.
- (Russian) Why do you need an equatorial mount and how does it differ from an azimuthal one.
Wikimedia Foundation. 2010.
See what an “Alt-azimuth mount” is in other dictionaries:
Telescope Equatorial mount Alto azimuth mount Dobsonian mount Mount (tool) File system mounting Mounting ... Wikipedia
German-type equatorial mount for an amateur telescope ... Wikipedia
The part of the Telescope on which its optical tube is mounted. M. t. allows you to direct it to the observed area of the sky, ensures the stability of its installation in the working position, and the convenience of performing observations of various types. Basic... ... Great Soviet Encyclopedia
Wooden Dobsonian mount with amateur telescope ... Wikipedia
Equatorial mount is a device for installing a telescope (or other astronomical instrument) so that one of the planes of its rotation is perpendicular to the earth's axis (and, accordingly, parallel to the celestial equator).... ... Wikipedia
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John Dobson in 2002 John Dobson (born September 14, 1915) is a renowned American amateur astronomer. Inventor of the telescope mount of the same name, which is in great demand among amateur astronomers. Also famous for his efforts... Wikipedia
In 2002, John Dobson (born September 14, 1915) is a renowned American amateur astronomer. Inventor of the telescope mount of the same name, which is in great demand among amateur astronomers. Also famous for his efforts in... ... Wikipedia