The mount for tracking
As we all know, the sky above us is apparently moving. The sun, the moon and stars are travelling every day from east to the west. This fact is not very practical in astrophotography especially because for deep-sky imaging the long exposures are obligatory. That means if we just put the camera to the usual tripod and make a one minute lasting exposition then we get just the star trails. The following video demonstrates the virtual rotation of the southern sky. The Megellan’s Clouds are visible also:
I believe that everybody understands what I mean.
However, this daily ritual of our home planet is not very appropriate for astrophotography. We need special mounts with tracking which tracks with just the same speed as the sky is moving. The Earth rotates quite slow so the stepper motors must track really slow and smooth to assure enough good tracking. All the bearings and gearwheels must be made very precisely to avoid any unpredictable jumps and so on. It is extremely important that we have a stable tripod or pier otherwise everything is worthless.
In general we three different types of mount: Alt-azimuth mount, German equatorial mount and Fork equatorial mount. All three has their advantages and disadvantages and every single of them I will describe in the following posts.
Stay tuned! 
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