Periodic checks (every 3-6 months):

: Use the optical plummet (if equipped) to center the instrument precisely over the ground station. Adjust tripod legs to bring the circular bubble near center. Use the three leveling foot-screws to precisely center the plate spirit level Rotate the instrument 90 raised to the composed with power

Do you have a Hilger Watts manual or theodolite story? Share your experience in the comments below (on the original blog post). Your knowledge could help another surveyor save a piece of history.

Built into the lower optical housing or tribrach, replacing the traditional plumb bob for centering the instrument perfectly over a ground station mark. Step-by-Step Setup Guide

Example: Circle shows 45°; micrometer reads 12' 30" → .

Turn these two footscrews simultaneously in opposite directions (both thumbs moving in, or both moving out) until the bubble is perfectly centered.

Rotate the instrument through 180 degrees. If the bubble remains centered, the instrument is level. If not, repeat the process to eliminate minor errors. Step 3: Focusing and Targeting

Unlike older plumb bobs, Hilger & Watts instruments pioneered the integrated optical plummet. The manual explains how to focus the eyepiece to ensure the instrument is centered exactly over the ground station. The Micrometer and Scale Reading