I've thought about this from time to time Eric, and I can't see much difference between keeping the scope outside covered with a thermal blanket and keeping it in a tin shed observatory, apart from security (
). The temp in a tin shed is easily going to get to the 40 deg mark easily. Check out some of this years Duckadang shots particularly h0ughy's scope tent, works a treat especially if you can get the one
without the zip strip that normally runs across the bottom of the door frame. Much easier to fit without having to lift it over the top of the scope.
Alternatively if you are worried about the scope you could always bring the scope in and leave the mount outside.