Forked Equatorial Telescope Mounts

Video Transcript

"This type of telescope is set up on a specific kind of mount, in fact is called a a a fork equatorial mount. So the fork refers to the two support tine that are actually holding the telescope itself. But the important part is the equatorial. As you'll notice, as I rotate this telescope it's not just moving straight up and over, it's actually rotating on an angle and that is a key feature in equatorial mounts and it plays a key role. If you watch the sun for instance rising over in the east, it doesn't come straight up and it doesn't move straight over. In fact, it comes up at an arc. This telescope, this telescopes mount should I say, is tilted so that it's actually rotating parallel to the earths axis. If for instance we had an altitude azimuth mount, where the telescope just simply rises up, moves over, up and over and you watch an object rise in the sky, you'll notice that it, when the object first rises it's mostly moving in the up direction or the altitude direction. And then it gradually moves over in the azimuth just a little bit. But then once it's pretty high in the sky it's mostly moving in azimuth. So what this means is, that as the object rises, the speed at which it changes it's altitude in azimuth varies over the entire path length. So that means that you would constantly have to adjust the speed of you telescope if you tried to track an altitude in azimuth. The nice thing about an equatorial mount is that since you're tilted with the earths axis and it's rotating at the same rate the earth rotates, it basically follows the objects at a constant rate. So instead of having to have a really complicated computer control to actually figure out how much to move in altitude in azimuth, you can install just a very basic clock drive in your telescope mount and that causes it to follow objects in the sky pretty much at a perfect rate. In order to set up a mount like this, you basically just need a compass. So a lot of the bases actually have compasses built in. And so the rotation axis simply has to point due north. So there's a point in the sky called the celestial pole where everything appears to rotate around that point. And that's where, when this telescope mount is aligned, that's where these tines will be pointing. After that you really don't have to level the base very much. As long as these tines are pointing at that one point in the sky this telescope will follow pretty much any object you place it on."