If in front of the objective you place a reflecting surface perpendicular ( ) to the telescope axis, the light will reflect back into the objective and form a real image of the cross hairs.
(the objective; place; you) (the light; will reflect; back into the objective) (the light; form; a real image of the cross hairs)
the objective the light the light
place will reflect form
you
back into the objective
a real image of the cross hairs