Should I Choose An Equatorial Or Altazimuth Mount?

by Russell Barker

In astronomy there are two types of telescope mount, the equatorial and the altazimuth. The easiest one is to use is the altazimuth mount, whilst the more technical and sometimes challenging one is an equatorial mount.

The altazimuth mount allows the scope to be pointed up, down and around, and is generally much lighter and mechanically simpler in construction. The major advantage of an altazimuth mount is the simplicity of its mechanical design.

Cheap and simple to use it remains a good choice for someone just getting into astronomy. The main drawback is in its inability to track astronomical objects as the Earth spins on its axis.

It's usually far more convenient to build a simple altazimuth mount and then use a computer to govern both axes to track an object, than to build a more mechanically complex equatorial mount which utilizes just a single motor.

For astrophotography however an additional motor is required to rotate the camera to match the field of view for long exposure photographs.

So if tracking celestial objects or astrophotography is what you intend to do an equatorial maybe the better choice.

Equatorial mounts are built to assist the observer to track celestial objects. These mounts come in a number of different variants to accommodate telescope weight, size, and slow motion or motor control.

It has its two axes aimed toward a point that allows you to follow a star or planet in your telescope’s eyepiece with just a single east-to-west motion and by the addition of a small motor the telescope is able to track stars automatically.

On the other hand, telescopes with alt-azimuth mounts, including Dobsonian reflectors, require that you move your telescope with both up-down and left-right motions to achieve exactly the same thing.

It is commonplace for the latest telescopes to incorporate clock drive mounts and computerized clock drives that enable the astrononomer to easily select objects by using a computer or hand held controller.

An equatorial does have a longer learning curve than the altazimuth and will require some time to setup and learn how to use properly, and its motions are not quite as user-friendly as those of an alta-zimuth.

Summary

1) Altazimuth: cheap, portable and easy to use. Can be used for astrophotograpy with the addition of accessories. Good for casual stargazing.

2) Equatorial: heavy, requires setting up, great for tracking celestial objects and astrophotography.