My ROR observatory is not completely sealed up so to keep dust, wind driven precip, and bird poop off the scopes I have covers on everything.
I use an all weather motorcycle cover on the C14. It works well for me because I park my scope in a horizontal position with the tube perpendicular to the counterweight bar. This approximates a motorcycle's shape with the tube as handlebars and the mount/counterweight bar as the body. The cover is shaped to fit a motorcycle.
For the 10" Starfinder on a GEM mount I use a Telegizmos cover--just the regular, not the 365. I also have a Telegizmos cover on the ST 120 and the PST. I got these covers from Astronomics.
All the covers are open at the bottom. If I am observing on consecutive days I usually keep the covers off. I never cover the scopes unless they are completely dry.