Hi everyone
I've been thinking about building an
observatory in my Sydney home's back yard before I put a permanent one up on Omaroo's high hill in clear dark sky. I guess we're just in Sydney more than we are down on the property.
My major problem with a traditional dome
observatory is that they unfortunately let everyone know what's in them as they exist only for one reason - to house expensive telescopes. I don't like the idea of relying on fibreglass doors to keep a determined criminal from taking my pride and joy and all the peripheral gear that goes with it.
So... I've decided on a variation of the roll-off
roof observatory that, for all intents and purposes, looks like nothing more than an innocuous garden shed. This design appeared in the May 1993 issue of Sky & Telescope, and was originally built by David Oesper in Ames, Iowa USA. He had trees at either end of his lawn in both due north and south directions, so the gables didn't get in his way. I'm going to make these either swing-down or removable on the one I build so that I get no interference in any direction. The door would have to be the height of the hinge line, but that's no matter. The beauty of this design for me is that most of my observing is done in a southerly direction, so I'd only ever need to
roll down just the half that covers that field of view, keeping wind and prying eyes to a minimum.
He build his with an isolated solid concrete pier that doesn't come into contact with the concrete floor to aid in vibration isolation. The pier is four feet deep in the earth. The floor is poured after the pier and after the lower part of the pier is wrapped in sponge neoprene to act as a gap seal.
The clever part are the hinged seconday outer walls, which support the eaves as the
roof counter-weighted section is rolled down, and which appear flush and part of the "shed" when locked up. These allow you to dispense with roller outriggers that are part and parcel of a horizontal roll-off
roof design.
The
roof sections rely on a rebated mortice at the apex of the gables to catch the top rollers, and then spring-loaded catches lock the two
roof panels in place. Pull the ropes attached to the catches and the
roof is free to
roll down.
I really like this design, so I'm going to draft some plans. I'll get together a materials manifest soon, and then document the build process if anyone else is interested in it.
I'd be really interested to hear what you have to say about it. I think it'll suit my particular needs, but it wouldn't be right for everyone I guess.
Cheers
Chris
Still got a bit of thought to go into it yet. I would prefer a Dome, but if I can get this method to work it will be worth building.
The third shot is heading up the hill that we plan to put the 
