It was generally a large quadrant, with one or two bars moving on a hinge,--to all intents and purposes a huge pair of compasses.

The direction of the sight was fixed by the use of a slit and a pointer, much as in the ordinary rifle.

This instrument was vastly improved by the use of a telescope, which not only allowed fainter objects to be seen, but especially enabled the sight to be accurately directed to the object observed.
The instruments of the pre-telescopic age reached their glory in the hands of Tycho Brahe.

He used magnificent instruments of the simple "pair of compasses" kind--circles, quadrants, and sextants.

These were for the most part ponderous fixed instruments of little or no use for the purposes of navigation.