Your main concern is moisture. Personally I would never leave the motors outside at all. Covering it up with a tarp won't be enough because of condensation build-up. Folks that have taken the trouble of building observatories or sliding roof types have heaters or lights to ward of moisture. Rust and corrosion (aluminum parts especially) will begin quite fast if not properly protected. Depending on the mount itself, that part is more vunerable than the OTA. If the tube is cardboard, then it needs to be properly "sealed" up like with paint or silicone. The mirrors won't be harmed, however condenstaion can leave water marks after awhile. You may consider building a small observatory or buy one of those domes (not tents). Of course you can tarp the mount, but make sure it is waterproofed and that "critters" cannot get in to build nests. Have fun and good luck!