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7' Dome Observatory Underway

Started by fugardi, 10/30/2004 09:14AM
Posted 10/30/2004 09:14AM Opening Post
Folks, I've been working on my observatory for almost 2 years now but having just broken by C11 tripod leg the night of the eclipse, I have been re-energized to say the least. Buying another cheapo tripod right now doesn't make sense for me. Anyway, I having been following all the great posts here and would appreciate any advice going forward.

I've got a used 7' homemade dome in decent condition (needs paint) waiting for walls. There's a 12" concrete pier with a used 4" steel pre-filled basketball poly down the middle. The foundation is approx 48" deep using around 36 or so bags of concrete. My plan is to top off the concrete with 4" of small gravel and pour an 8 foot DIA 4" concrete slab on top. I will pre-install 8" bolts (zinc painted with rustoleum) which will stick up thru the slab. I plan a PVC pipe under the slab to house the wiring. Walls will be 1" smaller in radius than the dome to allow a rubber rain guard to be mounted. Walls will be 2x3" approx 5' high with sheathing on the outside. 1/2" plywood will be cut in semicircles and glued/screwed together. The dome will rotate against skateboard wheels countersunk & mounted on the top circular plywood ring. I'd like to get the slab done before it gets cold.

Attached is a shot of the pier and dome

Steve Fugardi

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fugardi's attachment for post 19786
Posted 10/30/2004 09:14AM #1
2nd picture...

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fugardi's attachment for post 84375
Posted 10/31/2004 05:34AM | Edited 10/31/2004 05:49AM #2
This web site has an abundance of links to home observatories that should help.

My own thought is that an 8' diameter base will be small and you may want to consider a square 8' by 8' or larger that would offer space for shelves and a small desktop. Check out the following observatories in the above web site: Baker, The Birch Grove, Mill Creek, Pebble Beach, Sky Scape The Stirland, & Terra Rouge. I have a 10" dome on a circular base that has a 9' diameter inside the 2x4 framing. In hindsight a 10' by 10' square base would be roomier, but alas, it seemed right 20 years ago. Mine is on a raised deck set on 4' deep concrete piers. If I were to go with a slab, I would pour a concrete sill 1' high on the perimeter of the slab to keep the wooden wall off the ground & away from moisture unless PT lumber were used. I would also dig deeper around the perimeter and make the slab thicker in that area. I don't know the specifics of frost action on slabs, but you need to consider this as well as isolating it from your pier. I'm sure you've learned that vibration from walking on the slab can be transfered to the pier if in contact. Whatever base design you chose, the transition from base to dome will need to consider keeping out the weather, shedding water, and snow.
The dome apears to be fiberglass covered. If so, you may want to consider sanding the surface to remove the oxidised surface and recoat with appropriate resin and gelcoat rather than paint. If this cuts into the underlaying fiberglass cloth you may have to add another layer of glass cloth. If it is painted, then a good cleaning/sanding and repaint will surfice. It is easyier to redo the dome while it's at ground level. I just refinished the fiberglass surface on mine, up on ladders. Much harder that when I built it!