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Blogs Observatory Build Planning the Pier (part 1)
Blogs Observatory Build Planning the Pier (part 1)
16
Jun
2009
Blogs
Planning the Pier (part 1)
I don't really know what part of an observatory is truly the heart of the facility, but I'm pretty sure the telescope should be considered the top contender.
OK. So maybe not the best example. How about if I said, that the telescope is like a tree's leaves, in that it is effectively the center of the photo-synthetic process.
Think about it, a tree cannot survive without it's leaves (or in the case of coniferous trees; it's needles). The same is effectively true for an observatory, in that it cannot survive without a telescope. So if that would mean that the pier, is really not that different from a tree's trunk, and the trees roots, not that much different than the counter-sink.
So I bet you're thinking I'm going to mount the telescope on a tree!
Afraid Not.
I've done lots of research on the subject, reviewed many forums, had a chat with a local contractor, and spoken with some members of the RASC Winnipeg Centre, and I've learned the following:
OK. So maybe not the best example. How about if I said, that the telescope is like a tree's leaves, in that it is effectively the center of the photo-synthetic process.
Think about it, a tree cannot survive without it's leaves (or in the case of coniferous trees; it's needles). The same is effectively true for an observatory, in that it cannot survive without a telescope. So if that would mean that the pier, is really not that different from a tree's trunk, and the trees roots, not that much different than the counter-sink.
So I bet you're thinking I'm going to mount the telescope on a tree!
Afraid Not.
I've done lots of research on the subject, reviewed many forums, had a chat with a local contractor, and spoken with some members of the RASC Winnipeg Centre, and I've learned the following:
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The pier needs to be built such that it is equally as deep as the winter frost line
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The pier needs to be build such that it resists vibration
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The pier needs to be built so that sway is minimized
To meet these needs, I've come up with the following design:
This design is pretty simple. The "box" at the bottom is really just a solid chunk of concrete, with embedded rebar for reinforcement. The box will be roughly somewhere between 27 and 43 cubic feet, and will be positioned such that the very bottom is approximately 9.0 - 9.5 feet below grade. The reson for this positioning is that a local contractor indicated that the frost line in the region is rougly 8.0 feet below grade (or 6.0 feet in heavy trees). Therefore, by position the "box" half-above and half-below the frost line, I should be able to limit the amount of ground heave during the spring thaw.
The "tube" on top, which in this scale is roughly 7 feet tall, would be positioned flush with the ground surface. More than likely the tube will be 9 feet tall, resulting in 2 feet of the pillar exposed above grade.
All told, if the concrete box is 27 cubic feet, then it will weigh roughly 2000 Kilos, whereas with 43 cubic feet it will weigh roughly 3000 kilos. The concrete in the "tube", assuming a 12-inch diameter, will weigh roughly 500 kilos.
