Telescope Mounts For Astrophotography

Once again we will start with the basics of telescope mounts and the advantages and disadvantages of each type. We will then explore the particular features which are important for astrophotography.

A telescope mount's purpose, in simple terms, is to hold the telescope firmly and to provide a way to smoothly move the telescope. However for astrophotography purposes the mount needs to be more stable and be able to track the object you are trying image accurately. There are basically two types of telescope mounts though each has different variants. They are the altazimuth, and equatorial.


Altazimuth Mounts

These are the simplest, most basic styles of telescope mounts. They move in two directions for tracking, altitude (up/down) and azimuth (side to side) thus the name, AltAzimuth. Due to their simplicity they are cheaper (except in hi-tech computerized models). These mounts are fine for visual use, especially when using a short focal length telescope, but they are not very good for astrophotography except for planetary/lunar imaging. However the computerized mounts can be used for deep sky astrophotography if you are using a digital imager and keep your exposures short. More on this below. The three major variants of the altazimuth mount are:

Dobsonian; The 'Dob' was developed by John Dobson in the 1960's. A very simple design, with a flat platform on the ground, with a box on top of it where the scope is mounted. The box rotates on the platform for the azimuth motion and the telescope, which has circular 'hubs' attached to it, rotates in semi-circular cut outs into the top of the box for the altitude motion. Due to the simplicity and low cost of materials this style of telescope mount is the least expensive. You can spend more on a Newtonian telescope, with a large to very large mirror. Great for visual use but not at all usable for astrophotography. There are electronic tracking motors available for 'Dobs', even equatorial platforms, but this also increases the cost and thus you lose the price advantage.

Tripod Mounted Altazimuth; A more complex design than the 'Dobs' but still rather simple. Camera tripods are a very basic form of this mount type. There are also models made especially for telescopes which have slow-motion controls allowing you to track the object you are viewing fairly smoothly. Again the are fine for low-power, wide field visual use but they are not conducive to long exposure imaging. There are now also computer controlled mounts of this type which are fine for planetary/lunar work, but none that I have seen are usable for deep-sky astrophotography.

Fork Mounted Altazimuth; There are some computerized marvels in this design type but they are expensive. However with the electronics now available in this design you can get excellent results on planetary and lunar imaging especially with web cams. And you can also get good results on deep sky targets when using digital imaging equipment such as the Meade DSI, StarShoot Deep-Space CCD Color Imaging Camera, or a DSLR camera. You need to keep your exposures to 15 to 30 seconds, take multiple images, and then stack them. Again these mounts are costly.


Equatorial Telescope Mounts

These are the best telescope mounts for astrophotography bar-none when motorized. When accurately polar aligned you can take long exposures (although you will need to do some guiding corrections). The scope will only be moving on one axis (azimuth or right ascension) so it will track very steadily. It is also better for planetary imaging as the target will remain in the field of view for longer allowing you to take many images and then stack
them or if you are using a film camera to pick the best shot (when the atmosphere was nice and steady). There are two styles of this type of mount generally available commercially.

Fork Mounted Equatorial; Usually used on (physically) shorter telescope designs such as Schmidt Cassegrains and Maksutov Cassegrains. To make the fork mount equatorial you need to purchase a wedge so the scope can be polar aligned. I own a computerized model like this and get excellent results. However there is a drawback. When you start adding weight to the set-up with a guide scope or piggy-back camera, or your imaging equipment, you need to
add counter weights to achieve proper balance. This is more difficult with this design than with the 'GEM' which is reviewed below.

German Equatorial Mount (GEM); The best mount for astrophotography (in my humble opinion). There are two advantages to 'GEM's' in comparison to fork mounted set ups. Firstly achieving balance is a lot easier as this design already has counter weights included in the design. Plus the telescope body itself can be moved forward or
back on the mount to get the best balance. The second advantage is that you can mount different scopes on the mount where has with a fork mounted set-up you are stuck with the scope which came with the mounting.

A final tip, get the most stable tripod you can. The less vibrations and movement you can achieve the happier you will be with your astrophotography.

Clear Skies.

Telescopes For Astrophotography