There are two main types of telescope mounts that I am aware of, altazimuth (also known as alt/az) and equatorial. The mount is what holds the telescope body and fits on to a tripod or a permanent pier. The mount also determines how the telescope moves.

A telescope’s mount is very important if you aim to try your hand at astro imaging (something I found out the hard way as this wasn’t explained to me when I bought my first scope and mount). I’ll try and explain why this is important;-

Hope this isn’t too confusing… Find the star Polaris (if you’re in the Northern Hemisphere like me) in the night sky and you will see that from our perspective all the other stars etc appear to revolve around it in a circle. Because the Earth rotates once every 24 hours, take any star, for example Dubhe (one of the stars in the Big Dipper, also known as The Saucepan), look where Dubhe is at a particular time one night, say midnight, then look again at midnight the following night and Dubhe will be in almost exactly the same position (not exactly the same position though because the night sky gradually revolves around Polaris once every year as the Earth orbits the sun, meaning that Dubhe would have moved 180 degrees around Polaris six months later at midnight, and all the way back to where it started exactly a year later). Basically, what I’m trying to say is that objects in the night sky do not move in straight lines, and this is why your choice of mount is important for astro imaging.

My telescope is an 8” Meade LX200R which has a computer controlled electrically driven altazimuth mount. The name altazimuth is derived from the two planes the mount moves in – altitude (up and down) and azimuth (left and right). Objects close to Polaris appear to revolve around it in small circles. The further an object is away from Polaris the larger the circle it travels in around Polaris. So, for an altazimuth mount to follow an object in the sky the mount has to follow a circular motion by only going up and down, and left and right (this can be done by hand or by computer controlled electric motors in more expensive mounts). However, over time as the object moves in a circle around Polaris, the object will rotate in your eyepiece. This is perfectly fine for visual use but if you image with an altazimuth mount the image will rotate if you do long exposures, or a series of short exposures over a long period.



Having an altazimuth mount (pictured above) isn’t the end of the world though. Nobody told me about image rotation when I bought my scope and mount. I was so annoyed when I first tried imaging and every image had star trails as I’d not been informed this would happen and I obviously hadn’t worked it out myself. I later purchased a wedge which counteracts the rotation of the Earth, no more star trails! The wedge sits in between the altazimuth mount and your tripod or pier. Once on the wedge the telescope and mount have to be Polar Aligned which I’ll explain in another section.



Equatorial mounts (pictured below) are different in that they only need to be moved in one axis (as opposed to two in an altazimuth) as they are set up to be parallel to the Earth’s axis of rotation. This means a telescope on an equatorial mount will follow an object in the sky without inducing image rotation, and if it’s motorised it’ll only require one motor. I have never owned an equatorial mount so I can’t tell you too much about them.



If I was to start from scratch I’d probably opt for an equatorial mount over an altazimuth as I feel an equatorial is better suited to astro imaging. If you’re interested in buying a telescope and mount I’d suggest you visit a store and see the differences for yourself.