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An equatorial mount is primarily built the same as an altazimuth mount with one axis aligned parallel to the axis of rotation of Earth by pointing it at the North or South celestial pole.
This type of mount moves the telescope in two axes:
an equatorial mount, polar axis must be parallel with the rotational
axis of the Earth. For movement in the polar axis, the motor turns the mount at the same rate as the Earth's rotation. The declination axis is perpendicular to the polar axis. It is used to make adjustments in declination
– allows the telescope to be pointed at celestial objects of different
declinations. To keep the celestial object centred in the eyepiece, the
user needs to turn only the polar axis to track the object.
An equatorial mount allows the telescope to move in an arc that is perfect for tracking stars as they move across the sky.
Compared to an alt-az mount, the movement of an equatorial mount is continuous, which is perfect for:
This type of GoTo mount is straightforward to use and is suitable for beginners. Because of its simple design, it is much cheaper than an equatorial mount, which makes it appealing for amateurs in astronomy.
The most common types of the altazimuth GoTo mount are:
Altazimuth GoTo mount supports and moves the telescope in two different directions.
Two motors move the telescope separately:
Each axis is motorized and controlled by a computer.
To track an object, an altazimuth mount requires movement in both directions. Roughly speaking, tracking of an alt-az (altazimuth) mount can be visualized as a "zig-zag" motion. This type of tracking keeps the observed objects centred in the eyepiece. The problem is that all other objects in the field of view will rotate around the center of the field of view — this is called field rotation. Because of that, this type of mount is not very suitable for astrophotography
— it is impossible to take long exposure photographs without the effect
of field rotation. It is still possible to take beautiful sky images
with an altazimuth mount by taking multiple short exposure images and stacking them together with special software.
Altazimuth mounts can also be used for observing terrestrial objects.