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Telescope Mounts

Mounts are the KEY to successful astrophotography. While cameras, lenses and telescopes are important, a good mount is absolutely necessary. Excellent optics will not provide good images on a poor mount, but poor optics can produce stunning astrophotos on a good mount. The mount should be your #1 priority when considering your astrophotography setup.

The Altitude / Azimuth (ALT/AZ) mount is the most common mount for REGULAR photography. It provides a stable platform and protects your camera. The downside is that when a normal Alt/Az mount tracks the sky, it does not rotate your camera in the same manner the sky moves. More on this later.

You can, however, use the alt/az mount to produce Star Trail photos. These are photographs of the sky in which you WANT to let the stars trail as in the beautiful star trails above. You can read all about this technique in the TECHNIQUES section.

You can also use an ALT/AZ mount for short exposure astrophotography. When photographing planets, the Sun or the Moon, you can use a scope mounted on an ALT/AZ mount because the exposure times for these objects are so short that any rotation of the camera will not be noticed.

Why do I need to ROTATE the camera?

Many commercial telescopes are mounted on an ALT/AZ mount, and some even track objects across the sky. This works great for visual use, and they can keep an object in your eyepiece for very long periods of time. But they will NOT work for the long exposures required for deep-sky astrophotography. The reason is that ALT/AZ mounts move in a North/South, East/West or Up/Down, Left/Right direction. But the sky does not appear to move in those directions; it ROTATES around the celestial poles. To understand this, consider you are photographing the North Star - Polaris. Once you aim your ALT/AZ mount at Polaris, it will not need to move to keep the object in view. Polaris moves in such a small amount, that it appears stationary in the sky to the naked eye.... all night long. But the stars around Polaris rotate once per day around it. Your mount will not move, and if it did, it can not rotate, but only up/down, left/right.

Consider you are looking at the constellation Cassiopeia in the Northern Sky.

Note the angle that Cassiopeai is. Now watch what happens after several hours.

Cassiopeai has moved to the left (East), but more importantly it has ROTATED too. When you add equatorial grid lines, you can see the arc that every object follows in the sky as the Earth rotates.

Now you can see how Polaris seems to be still, and every other object revolves around it. Your ALT/AZ mount can not compensate for this! What you need is a mount that moves in the exact same arc as the sky... and the Equatorial Mount will do just that! (next chapter)