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In the days before go to mounts, and electronic star maps, the telrad was a useful tool for finding stuff, not just for pointing the scope at a spot, as in a rdf.. the rings of the telrad show .5, 2 and 4 degree circles. When a known star is found, the position of a desired target can be located by ‘Star hopping’ to other stars along the way. Utilising a star chart, one can locate intermediate stars and their distance from each of the others along the way, noting their separation in degrees. The telrad allows one to try to identify these intermediate stars using the rings as a guide to their angular separation. Having found an intermediate star, it can be centred in the scope, and then using the telrad, locate the subsequent stars until eventually getting to the desired target.
These days, with go to mounts, Argo Navis , and electronic charts, the telrad is slow and cumbersome. Like moving from log tables to a scientific calculator.
Some however, enjoy the search without the aid of electronics.
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