Quadrant (instrument) - Framed Quadrant

Framed Quadrant

Large frame quadrants were used for astronomical measurements, notably determining the altitude of celestial objects. They could be permanent installations, such as mural quadrants. Smaller quadrants could be moved. Like the similar astronomical sextants, they could be used in a vertical plane or made adjustable for any plane.

When set on a pedestal or other mount, they could be used to measure the angular distance between any two celestial objects.

The details on their construction and use are essentially the same as those of the astronomical sextants; refer to that article for details.

Navy: Used to gauge elevation on ships cannon, the quadrant had to be placed on each gun's trunnion in order to judge rangs, after the loading. The reading was taken at the top of the ship's roll, the gun adjusted,and checked, again at he top of the roll, and he went to the next gun, until all that were going to be fired were ready. The ship's Gunner was informed, who in turn informed the captain...You may fire when ready...at the next high roll, the cannon would be fired.

In more modern applications, the quadrant is attached to the trunion ring or of a large naval gun to alighn it to benchmarks welded to the ship's deck. This is done to ensure firing of the gun hasn't "warped the deck." A flat surface on the mount gunhouse or turret is also checked against benchmarks, also, to ensure large bearings and/or bearing races haven't changed... to "calibrate" the gun.