Ah, good point. It will also give a reference point as to where the dome should be when you exit. I haven't had much experience in observatories, but the few times I have I got disorientated because the limited vision. When it was time to leave I found it hard to locate the door
Of course when it is your own dome, you become used to it I suppose.
Cheers
Tony
Chris, some of the designs I have seen, there is a separate room with a roof, sometimes a door so can be heated without much interference with the scope and imaging, an example here
http://www.iceinspace.com.au/forum/s...t=92644&page=2