star tracker

A star tracker is a motorized mount for cameras.

Star trackers are used in astrophotography (photography of the night sky) to compensate for the rotation of the earth. Without use of a star tracker, anything but the shortest shutter speeds render each star in the night sky as a “star trail” rather than as a dot.

Star trail photographs can qualify as TTG but must be made with a single uninterrupted exposure, as per P5.

(Many star trail photographs seen online incorporate an additional exposure for the earth-landscape portion of the image, disqualifying them from P5 and thus from TTG.)

Star tracking is just another means of panning — albeit panning very slowly — which is why star tracking is allowed by TTG when used to make single-exposure photographs (as per P3).

However, multiple-exposure photographs made with a star tracker are disqualified by #2 in P3, like any other multiple-exposure photographs made while panning.