Properties:

A telescopic instrument used in determination of wind direction and speed by optical tracking of free moving balloons. Two telescopes are generally provided, one for finding the object and the other for tracking. Sighting through the scopes is by means of right angle eyepieces. Vernier scales are used for fine reading of the horizontal and vertical circles. Some instruments are designed with auxiliary devices for plotting the observed positions at the time of observations. Illumination may be provided for observations at night. Excludes transit and transit, pocket.