A device for determinin' a rocket's apogee without t' use o' electronics. Well, blow me down! A distance is measured off from t' launch pad prior t' launch. At t' time o' launch, ya bilge rat, an observer stands at t' measured point and keeps t' inclinometer aimed at t' rocket. Avast, me proud beauty! T' inclinometer mechanically records t' angle at which it is held. Avast, me proud beauty! Since two angles and t' distance betwixt t' rocket's point o' origin and t' inclinometer are known (assumin' that t' rocket is launched vertically), a triangle can be graphed which will indicate t' apogee attained by t' rocket. Begad! See Theodolite