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I’ve just heard that the Australian continent is moving North at an alarming rate. No wonder I’ve been having trouble with my guiding! I gather it’s moving so fast that the GPS system can’t keep up with it. Maybe we’ll be able to shoot some Northern hemisphere targets soon! Enjoy. |
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| So much for my North/South string line in the backyard. |
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Well, the eastern plate seems to be moving north at a rate of 5.6 cm per year. Look at it this way. Next time you decide to do a project with one millennium of integration time, maybe it could provide some natural dithering of sorts?  |
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Next time you decide to do a project with one millennium of integration time, maybe it could provide some natural dithering of sorts? Unfortunately this is drift, so it will create walking (drifting) noise and mess up polar alignment. On the bright side, you will soon be able to use Polaris for polar alignment.  Cheers, Wim |
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Wim van Berlo:Next time you decide to do a project with one millennium of integration time, maybe it could provide some natural dithering of sorts? I'm sorry to point out that once you see Polaris from Australia, the celestial pole will no longer be in the vicinity of Polaris ... |
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'm sorry to point out that once you see Polaris from Australia, the celestial pole will no longer be in the vicinity of Polaris ... This is only true if the reason it happens is due to change in where Earth's axis of rotation points or drift by Polaris. And indeed, other bright stars have been closer to the celestial north pole in recorded history. If Australia itself suddenly moved to the Northern Hemisphere, the location of the celestial pole wouldn't change. |
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| Alpha Draconis was the Pole Star 5 thousands years ago. But who recorded it? |
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| Thanks for the chuckle, greatly appreciated. |
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Wim van Berlo:Next time you decide to do a project with one millennium of integration time, maybe it could provide some natural dithering of sorts? If Neil sets up his gear for a 1000-year integration project, I'm afraid that all of us will have worse problems than walking noise and polar alignment by the time it's done. The good news is that since the moon is going one inch further away from Earth every year, lunar light pollution will be 0.0000001% less severe by the time his project is wrapping up. |
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andrea tasselli: Hahaha ... *checks notes* ... not me  "The continent is moving north by about 7 centimetres each year, colliding with the Pacific Plate, which is moving west about 11 centimetres each year" ... so we are in a head on collision? The Earth spheroid radius ranges from a maximum of nearly 6,378 km (3,963 mi) at the equator. So if my math is correct that 7cm (north btw) but let's assume east is 0.07/40,023,857*360 = 2.27mas (milli arc seconds) per year. If your mount tracks to less than 0.1 arcseconds over the course of 1 hr then the tectonic movement is in the order of micro arcseconds ... so about a millionth of a pixel.  |
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Well, as one might expect, the mathematicians have saved the day with their maths and there is no immediate need for concern. In any case, Australia is well shaped for a collision to the North. I was also going to suggest that the “CS” wish should be for “Continental Stability” down here! Oh, and someone once told me they thought “Continental Drift” was a dance from the 1960’s. I’m sure that’s quite enough! |
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Peter:andrea tasselli: So if you had a mount on a pier in the ground, how much would your polar alignment be out in a year if we are moving 7cm north east (and if not out enough to matter re polar alignment, how many years before it matters?) |
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| In about 1,555,217.4 years your polar alignment would became from "good" to just "fair". |
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How did you calculate that? I'm also thinking good can mean different things to different people. |
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This is a real problem. I wonder if we can see the different directions of continental drift in ground-based red shift measurements of galaxies??? Maybe this explains the discrepancies in the Hubble constant. I'll draft a paper for Nature. |
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I was wondering if anyone had experimented and polar aligned, dragged their mount 7cm north east and then looked at polar alignment (maybe sharpcap each time) I was wondering just in case I was able to eventually have a place where I could set up a pier. |
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Greg McCall: 3' off from good, good meaning 3' or less from true pole. |
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I don't believe it! I don't believe anything! I even don't believe that I don't believe it! Do you believe me? |
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I'm glad I finally got some "sensible" replies! Thanks, Neil |
