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MI-500, MI-750, and MI-1000 Telescope Mountings

German and Fork Equatorial Mounts

The MI-500, MI-750, and MI-1000 mounts are available in a German equatorial and an equatorial fork configuration. The MI polar cone and base are identical in either configuration. The polar cone houses the right ascension axis with drive gear and DC servo motor. The polar base supports the cone, and includes azimuth and altitude controls for polar alignment.

For a German mount, the declination assembly attaches to the top of the right ascension axis. For a fork mount, the fork arms and central hub attach to the top of the right ascension axis. A single mount can, in fact, be converted from a "fork to German" or "German to fork" configuration by adding the appropriate declination assembly.

Each type of mount has distinct advantages and limitations. The long debate between the advocates of fork mounts and German mount enthusiasts has no winner. Choosing the appropriate design will depend on the type, weight, and dimensions of the telescope tube assembly.
Polar Cone and Base

German Equatorial

The German equatorial design is a classic telescope mounting that is capable of handling a wide variety of telescope tube assemblies. By simply changing the position of the counterweights, a variety of equipment can be easily attached to mount.

Since the center of mass of the optical tube assembly is usually near the center of the supporting column or pier, a German mount can generally carry a heavier load than the equivalent fork mount. German equatorial mounts can easily handle the long tubes of refractors and Newtonian telescopes.

One disadvantage of the German design is the need to "flip" the telescope tube when the object you are observing passes through the meridian. With its long declination axis and heavy counter-weights, a German mounting has a large footprint, and the focal plane of the telescope can sometimes be in an awkward observing position.
German Equatorial Configuration

Equatorial Fork

The Equatorial Fork configuration is excellent at holding compact tube assemblies. Unlike the German mounting, a fork mount tracks objects continuously through the meridian. These mounting are often used with Cassegrain optical systems. Fork mounts provide easy access to the telescope focal plane, which is usually a short distance below the declination axis, which passes through the upper ends of the fork arms.

Since fork mounts do not need the large counter-weights of the German mount, fork mounts are usually more compact and transportable.

However, fork mounts have a smaller load capacity than the equivalent German mount, since the telescope tube is suspended far from the center of the mount column or pier. Also, fork mounts are machined for a specific arm separation, making these mounts less versatile at handling a variety of telescope equipment. The short length of the fork arms does not accommodate the long tubes of refractors and Newtonian telescopes.
Equatorial Fork Configuration

Last Updated: January 12, 2007

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