reading-telescope

from The Century Dictionary.

• noun A telescope used in reading a scale placed at a distance or reflected in a mirror.
• noun Specifically, a simple form of cathetometer. It consists of a telescope which has an object-lens and a negative eyepiece containing a spider-line or cross-wire. A level is attached to the top of the telescope, which may stand on a tripod or be movable about and up and down a vertical standard.