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quote:
Originally posted by kalianna
I checked both the regular usgs site and the HVO earhquake sites right after that 4.4. It took them 15 min. to post it. And, by the way, the coquis didn't let up for a moment so forget THAT early warning system.
There's been so many quakes at this point, I think the coquis are like eff it, what's the point?
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"
When the shear pins break, what does it rest on ? Is it protected from multiple quakes after that?
Is it resting on a more forgiving surface until' it can be remounted with new pins ?
Will all this jostling around cause errors in data or break up consistency ?
ETA:
For anyone wondering:
http://www.ukirt.hawaii.edu/telescope/sky_access.html"
The telescope mount (the whole structure that supports the mirror) rests on large ball-bearings. It's finely balanced and am not concerned too much about damage to the structure, but the shear pins breaking indicates the whole thing has shifted slightly (probably a millimeter or less). It's still on the bearings though. Unfortunately, a millimeter of shift at that point means we'll be way off when pointing at targets and will have to recalibrate the telescope. It'll be virtually impossible to carry out science observations until that's done as we won't know what we're pointing at.
When new pins need to be inserted, the telescope is literally jacked up and new pins inserted. There's a video about this taken from an astronomer many years ago (from memory, he gets things wrong when he says the pins hold the telescope in place - they don't, they just tell us if something moved).
https://youtu.be/yn5pHqENfJA
PS. If you watch the video from about the 5-minute part, you'll see why I don't want people replacing the shear pins when there's a good chance of another severe earthquake.
So the structure is over built and the shear pins are the sacrificial.
How do you confirm reset of position ?
How to know if the land shifts under the whole footprint ?
If it happens, how to measure back to square one so to speak?
Do you reverse engineer the position USING star info ?
Even if only to confirm the reset on the jilted mounts ?
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"Do you reverse engineer the position USING star info ?"
That's pretty much it - we'll first spend time trying to find something we recognize in space, set the base pointing and then spend time slewing the telescope all around the sky measuring the telescope position using accurate star positions. That goes into a software model which will then be used to point the telescope within about 0.5 arcseconds of where we want to look.
If we can't do that, then something is badly wrong, but have never known that to happen due to an earthquake. Before we even do this though, the whole observatory: building, dome and telescope will be checked out to ensure every moving bit and the structure works.
Isn't it frustrating to know you can never make something perfect twice?
