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Old 11-10-2018, 12:16 PM
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Sandy Ridge Observatory

ChrisM is offline
Join Date: Mar 2008
Location: Gippsland, VIC
Posts: 711
Originally Posted by lazjen View Post
The dome has been dismantled today and taken away to be refurbished (and upgraded) before it goes to the new location.

I am in the last stages of sorting out the design of the new setup with the builders. I'm going for something like Neil's setup, adjusted for the slope I'm on (also no enclosed panels for the lower half). On the top side, I'll have a ramp to a small landing outside the dome that will have a small air gap to the dome's decking to avoid water seepage issues. The landing will be enough to open the door and to have an easy level place to step onto when coming in/out of the dome in the dark.


1. My current plan for the central pier is to have the concrete come up to about 250mm above the deck floor height (and then put a metal pier on top of that). I'm planning to have one of the electrical/data conduits come up with this pier, so I'll have some space on the side of the concrete to place power and data outlet for mount and other gear (there will be separate conduits on the deck itself to supply power and data to other items). Exact dimensions haven't been determined yet, but it's currently projected to be 500 mm in diameter, 2m high with a depth of 900mm (the builder has suggested 600m depth for the rest of the deck for comparison). Any problems with this?

2. For the 3 bolts I'll embed in the top of the concrete pier. What size should they be? I've been considering 18 to 20mm threaded rods, about 1m in length? How much should I leave protruding from the cement for securing a metal pier (which I have yet to obtain)? And for the placement - what's the ideal location, i.e. the distance in from the outer edge, given the 500mm diameter mentioned above?
Hi Chris, just seen your queries and probably a bit late for a reply, but here's what I did:

Like Neil said, bigger can be better (very impressive work, Neil), so I dug a 2 cubic metre hole for the reinforced concrete pier base; the pier is 450 dia x ~2.2 metres in height. I designed the pier to come up to about 150 mm below observing floor level, and made the bolted connections to the steel pier there. From memory, the 8 bolts (actually probably threaded rod) that I set into the top of the pier were into the concrete by only about 300 mm and had very large flat washers on their bottom ends. I think that they were half-inch size, and gal.

Here's a link to my construction thread:

and also a link to a more detailed construction article that I wrote for NACAA:

Looking forward to seeing your progress.

Cheers, Chris
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