Finish line in sight
After just over 1 year the observatory is finally nearing completion! All that remains is to install the dome and pier and it will be ready for observing.
The Nexdome finally arrived many months after ordering. The box came a bit banged up (it came all the way from Canada via Australia!) but everything inside appears to be intact and undamaged. It seems to have come short of a few nuts/bolts but this shouldn't pose a major obstacle even if it is a bit annoying. The instructions are also somewhat skint on detail but I think I've got a good grasp on how to assemble it. As long as all the bolt holes line up it will be easy but I wouldn't be surprised if I end up having to drill some new ones. The hardest part will be getting it up into position as the observatory roof is too steep to stand on. I may just assemble it up there from the inside but that will also be a bit awkward. We'll see how it goes.
The gap at the top of the roof isn't big enough to fit the dome so we've had to produce a wood ring to provide a wider platform for it to sit on. Affixing it will be a simple matter of screwing it down to the roof along the inside diameter then the dome's base ring can be screwed down along the outer. The ring provides a little bit of extra width to help center the dome with the pier. I'm not sure how important it is to do this but I want to get it as close as possible as I presume it will help with dome automation accuracy in future.
To get the dome centered though, I need to have the pier in place. After looking at the price of existing piers I figured I'd probably save a lot getting an engineer to do a custom job for me. I put together a wooden prototype pier (see image below) to help illustrate what I'm looking for. The prototype doesn't include a top plate or its bolts so you'll have to use your imagination for that.
After consulting with a couple of local engineers we've decided to adjust the design to one that uses rods rather than intersecting plates. This uses less steel and should save a lot on cost while still being fit for purpose. Provided it's steady, as the engineers assure me it will be, I actually prefer this design, even over the traditional pipe. It allows access under the plates which could be useful. For the moment I don't plan to use a pier adapter plate for the mount and will just sit the cradle from the top of the mounts tripod on the top plate. Having space under the plates means I will be able to use the rod that came with the mount to secure it. With a more standard pier design this would not be possible (not that that would be a big deal anyway).
The pier should be finished any day now and after it's done I'll be waiting for a fine day without wind to get out there and finish the job. Once the roof is off, the building is exposed to the elements so we'll need to do it all in one go. Everything going to plan I suspect it'll be only a few hours work but rarely have we not encountered unexpected challenges in this process! Next update will follow once the pier is completed.