An astrogator was a device used for navigation, common on Template:ShipClass starships. (TOS: "The Gamesters of Triskelion") Located between the helm and navigation stations at the forward section of the bridge, the helmsman could change the ship's heading simply by turning the dial upon the face of the astrogator. (TOS: "And the Children Shall Lead")
Although Franz Joseph's Star Fleet Technical Manual described this navigational device as an "astrogator," it was never actually described as such in dialogue in any Star Trek episode or film.
The astrogator of the USS Enterprise
The astrogator of the USS Defiant
The astrogator on the alternate USS Enterprise