To anyone who has any doubt that unheated dew caps can help keep dew and frost at bay: I just closed my observatory after another fruitless night of hunting (you'd think that at least one of the 250+ galaxies I imaged tonight would have the common decency to harbor a supernova <g> ). After over 7 hours of operations the walls of my observatory were covered with frost, as was the mount, telescope and even the outside of the dew cap. But barely a hint of frost on the corrector. Night, night, patrick