Zenith Telescopes
Some telescopes designed to measure star transits are zenith telescopes designed to point straight up at or near the zenith for extreme precision measurement of star positions. They use a altazimuth mount, instead of a meridian circle, fitted with leveling screws. Extremely sensitive levels are attached to the telescope mount to make angle measurements and the telescope has an eyepiece fitted with a micrometer.
Read more about this topic: Meridian Circle