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Almost as important as choosing the right telescope is choosing the right mount. A wobbly mount can ruin your beautiful night no matter how good your telescope can perform. The same goes with hard to operate mounts especially if you’re not that technically inclined. On the other hand, a good mount can augment your stargazing experience a lot even you have a not-so-good telescope.In this article, we will try to show you the pros and cons of some of the most popular telescope mounts. There are generally two types of mounts - the alt-azimuth mount and the equatorial mount. Both have their advantages and disadvantages depending on your observational needs as well as your technical skills.

The Alt-Azimuth Mount

The Alt-Azimuth Mount or Alt-Az is simpler compared to the Equatorial mount. Basically it allows you to move your telescope on an up-down (Altitude), left-right (Azimuth) direction. An Alt-Az mount is easy to setup - you just basically put it on the ground and point your telescope to the object that you want to observe. It is also lightweight and the least expensive. If your target moves away from your field of view (FOV), all you need to do is adjust your telescope to point to it again in an up-down, left-right direction.

One famous Alt-Az mount is the Dobsonian mount. It’s famous because it’s simple to build thus making it an effective low-cost mount for casual observers. It also allows for easy setting up of large aperture scopes. I saw a friend who simply placed his 8-inch newtonian optical tube on top of his dobsonian mount and that’s it! I also saw a full 12-inch newtonian telescope operate relatively easy on a dobsonian mount.

The problem however with Alt-Az mounts is that it they don’t compensate with the earth’s rotation meaning you have to move it in two different axes most of the time just to keep your target within the FOV - especially if the object you’re viewing is far from the celestial equator. The farther your target is from the celestial equator, the more difficult it is to track it with an Alt-Az mount. This problem increases ten-fold if you’re viewing objects at high magnification.

The Equatorial Mount

On the other hand, we have the equatorial mount. It is bulky, complex, and heavy but all those negativities are washed out when you start observing - that is if you haven’t been clouded out yet considering the time you need to consume just to setup an equatorial mount.

An Equatorial (EQ) mount is positioned so that one axis is pointing to the celestial pole which is roughly the star Polaris in the northern hemisphere. This axis is called the Right Ascencion or R.A. axis. The other axis is called the Declination or Dec axis. The declination axis allows you to change the ‘height’ of the scope. To make it simpler, an EQ mount is simply an Alt-Az mount with it’s Azimuth axis pointing directly at one of the celestial poles. In this configuration, the setup will obviously be out of balance thus requiring it to have counterweights on the other side. The counterweight should at least be as heavy as the telescope thus doubling the weight of a scope with an EQ mount.

The beauty however of an EQ mount is that once you’ve aligned the R.A. axis to the celestial pole and you have found your object in the sky, all you need to move is the Declination axis as opposed to moving the Altitude and Azimuth axes in an Alt-Az mount. This makes an EQ mount relatively easy to operate when tracking objects at high magnification. When equipped with a small motor attached to it’s R.A. axis, the EQ mount becomes a perfect mount for astrophotography as it will continously put the object being tracked in the center of the the FOV as the motor counteracts the rotation of the Earth.

Popular EQ mounts are the German Equatorial mount and the Fork mount. The German Equatorial mounts are the ones you see with counterweights on it. Fork mounts don’t have counter-weights but usually have a heavy metal plate positioned off-centre to maintain the stability of the scope.

Note of interest on Fork Mounts:

Fork mounts are usually thought of as an Equatorial mount but it is also worth noting that it can also be used as an Alt-Az mount.

Fork Equatorial Mount

Fork Alt-Azimuth Mount

So what mount should you choose?

With the popularity of Go-To systems nowadays where you can simply punch in the name of the star, planet or DSO that you want to observe, choosing the right mount becomes almost trivial. But then, not all of us can still afford these Go-To systems. Furthermore, some of us would rather spend the extra money on another good eyepiece.

So, what would you choose? My suggestion are as follows…

Choose an Alt-Az mount if:
* You want a lighweight and affordable mount
* You want an easy to setup mount
* You just want to enjoy the night sky without all the technical hassles

Choose an EQ mount if:
* You want to view stuff at high magnification
* You need tracking of objects for a longer period of time
* You’re into astrophotography (R.A. motor needed)

Alt-Az mounts are generally good for beginners but as your interest in astronomy grows deeper, the EQ mount would most likely do better.

Clear skies to all!

Mike Lopez if a member of the Astronomical League of the Philippines and maintains a website on different topics at www.mikelopez.info. Mike Lopez also provides web hosting services at www.sydel.net.

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