observatory

I am just beginning to plan out an observatory at my house.
I will remove a closet that is unused, put a doorway in and that will
go to a short set of steps up to a platform at the rooftop.
I was wondering if anyone had plans or recommendations for a small
observation platform where i could place a 12 or 14" reflector type
telescope and leave it there knowing it will be protected from
wind/rain and sometimes snow (This means a opening/closing roof)
Thanks
Eric