I know that mirror and tube cool down is important. It seems like most of the questions revolve around bringing a scope from a warm house into the cool outdoors requiring a certain cool down period. But what if the scope is kept in an unheated environment like a garage? Around here in the summer time, the air temp can cool from, say 85 F down to 55 by viewing time, maybe a 5 or 6 hour period. That is something like a 6 degree per hour rate. Winter evening cooling can be even steeper when the sky is clear. I'm especially interested in 8 or 10" scopes, but would welcome a general discussion of ambient cooling rates because I intend to keep my scope in an unheated environment year-round.
I guess my question is, is there a certain cooling rate in terms of degrees/hr for a given mirror size or telescope type that is acceptable to avoid problems?