188 Auto Reflection Target
Fits Brunson-type Transits
The model 188 is a multiple paired-line glass target used with transits or levels equipped for autocollimation (having a light source).
Slipped on the objective end of the instrument, it allows the setting of the telescope perpendicular to a mirror. Adjustments are provided to permit centering the target pattern on the optical axis of the transit (two opposing pairs of setscrews set at right angles allow you to adjust the position of the glass target).