Can someone tell me the purpose of commander cupola on a tank?
I am building a E-100 kit (Dragon Maus turret) and thinking of adding a commander cupola...but then there are already 2 periscope on the top of the turret which got me thinking.. should I add a commander cupola since it already have the scopes...if I do add one should I remove one of the scopes.

The cupola gives the tc a 360 degree view while under cover of armuor. A single periscope ,usualy with an armoured cover only gives a few degrees view left and right. To kill the enemy , you have to see the enemy.And sticking your head out the hatch while under fire by artillery or in urban / wooded areas ( snipers ) is a good way to get killed.