Schneider 120mm L/28 long gun sight
The 120mm Schneider long guns adopted by the Bulgarian Army in 1897 was equipped with a goniometer γ graduated in millièmes, a telescope L and a collimateur K, which was mounted on the telescope side and was able to move around the axis α. The whole sighting apparatus was carried by the cradle sector Σ turning on the right trunnion and directed by means of the elevating handwheel G. The sector Σ could be shifted by means of the little handwheel Γ through a spiral gear and the elevating rack k. The two handwheels G and Γ were carried by a bracket of the carriage. A vernier graduated scale V, placed at the end of one of the cradle arms, could be shifted in front of the graduation in milliemes of the sector Σ.
To aim with direct fire, direct the optical axis of the telescope to the target by means of the handwheel Γ and bring the zero of the graduated scale V was in front of the graduation corresponding with the desired range by means of the handwheel G.
To aim with indirect fire, first shift the sector Σ to bring between its marks the spirit level N set in advance to correct the sight angle; then, like before, bring the zero of the graduated scale V in front of the graduation corresponding with the range by means of the handwheel G.
To aim at moving targets, disengage the spiral gear by means of the lever m, connect the sector Σ with the graduated scale V, so that the zero was brought in front of the graduation corresponding with the range and finally aim the gun with the bar sight as for direct fire.
To aim the gun at a target placed on a different height the collimateur k’ was employed.
CUREY. Charles Marie : “L’artillerie Schneider-Canet à l’exposition universelle de 1900”. Revue d’artillerie : LIX (Octobre 1900 – Mars 1901), pp. 161-163.