An equatorial mount is a type of telescope mount used in astronomy that is designed to follow the apparent motion of the stars in the sky caused by the rotation of the Earth. It consists of two perpendicular axes: the right ascension (RA) axis, which points towards the celestial pole and moves in a circle around it, and the declination (Dec) axis, which is perpendicular to the RA axis and moves up and down along it.

The RA axis of the mount is usually aligned with the celestial pole, allowing the telescope to track stars as they appear to move across the sky due to the Earth’s rotation. By using an equatorial mount, an observer can keep a celestial object in the field of view of the telescope for long periods of time, allowing for extended observations or astrophotography.

Equatorial mounts can be manually operated or motorized, with the latter often being preferred for long-exposure astrophotography. Some mounts also include features such as computerized GoTo systems, which can automatically locate and track celestial objects based on input from a computer or hand controller.

Equatorial mounts come in various sizes and designs to accommodate different telescopes and setups. They are commonly used for astrophotography, especially for deep-sky imaging where long exposure times are necessary. However, they can also be used for visual observation of celestial objects.

A different kind of mount that you may encounter is an Alt-Az mount, short for Altitude-Azimuth mount. This is a type of telescope mount used in astronomy that moves the telescope along two perpendicular axes, one for altitude and one for azimuth. The altitude axis tilts the telescope up and down, while the azimuth axis rotates it side to side.

Unlike an equatorial mount, an Alt-Az mount does not have a fixed orientation with respect to the celestial sphere, and thus does not track the apparent motion of the stars. Instead, it moves the telescope directly to the desired position in the sky, which makes it easier to use for visual observing and shorter exposures for astrophotography. Alt-Az mounts are often used for observations of the moon, planets, and other objects that move relatively quickly across the sky.

Alt-Az mounts come in various sizes and designs to accommodate different telescopes and setups. They are often simpler and less expensive than equatorial mounts, making them a popular choice for beginners and for portable telescopes that are easy to transport. However, they are not useful for long-exposure astrophotography of deep-sky objects, which require the more precise tracking provided by an equatorial mount.

Some Alt-Az mounts (specifically the Az-Gti) allow loading alternative firmware to convert them to an Equatorial mount with the addition of a cheap Equatorial wedge.