Syntax:  center {<expression>}
         centre {<expression>}

The RasMol centre command defines the point about which the rotate command and the scroll bars rotate the current molecule. Without a parameter the centre command resets the centre of rotation to be the centre of gravity of the molecule. If an atom expression is specified, RasMol rotates the molecule about the centre of gravity of the set of atoms specified by the expression. Hence, if a single atom is specified by the expression, that atom will remain `stationary' during rotations.

Type help expression for more information on RasMol atom expressions.