Most of the cannons of that time didn't have aiming tools except from the knowledge of the senior gunner operating his cannon squad.
With the coordenation of the captain and the gunnery officer they adjust there aim, By firing a ranging shot they see what they are aiming at and adjust the firing ark, and most of the senior gunners knew there cannons because they have had lots of exercising with it, so sorry but the most cannons looked like this, without any aiming mechanism:
(Talking about 1750-60 Era.)