GOH-A dovetail goniometers are made from solid brass and are available in 15-, 25-, 40-, 60- and 65-mm square platform sizes. They are driven by a high-tolerance worm-gear mechanism which yields angular position readable to less than 12 arc minutes using the vernier scale. As with all goniometers, the axis of rotation is situated parallel to and above the mounting platform. Opto Sigma goniometers of like-size are designed to be stacked so that they have intersecting orthogonal axes of rotation. In this configuration, they have capability for orbit-like positioning about a single point. The GOH series of goniometers are lockable and finished in a flawless RoHS-compliant super black chrome.