How do I use the latitude adjustment screws on my Advanced GT mount?
November 3, 2008
The base of the Advanced GT mount has two screws mounted opposite to one another that are used to adjust the tilt of the polar axis. The rear screw (underneath the lower end of the polar axle) is opposite the counterweight and normally bears the weight of the equatorial head. The front screw locks in the latitude adjustment.
The polar axis of an equatorially mounted scope must point at or be polar-aligned to the north celestial pole, the point in the sky around which all the other stars appear to rotate. The pole is directly above the north point on the horizon. So your axis must point both north and also be tilted up at an angle. Since the altitude of the north celestial pole is always equal to your latitude on the earth, you can just use the scope’s latitude adjustment to raise the polar axis to the right angle. This can be done during the day before an observing session.
To increase the latitude, loosen (unscrew) the front screw and tighten (screw into the mount) the rear screw until the latitude index arrow is pointing to your latitude. If the head doesn’t move as the screw is turned, push it so it bears against the rear screw. Tighten the front screw to lock it when the desired latitude is reached. To lower the latitude, unscrew the rear screw.