Setting Latitude : Aten II shown, other models similar.
In order to set Latitude: first, loosen the 3 socket head screws (A) that clamp the base onto the latitude ring. Next, tighten the set screws (B) to force the clamp to release the latitude ring, allowing movement. Position the numerals on the ring where your latitude lines up with the back edge of the clamp (C). The numbers engraved on the latitude ring denote the value of the major line to their immediate left. Increments are in 1 degree with major lines every 10 degrees.
Once set, loosen the set screws, then tighten the socket head screws to clamp the latitude ring.
Note: Aluminum products are fitted with 1 release set screw, in the top position.
The latitude shown in the illustration indicates 55 degrees.
Here is a photo of this adjustment on an Aten II:
