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Anthonyexmouth

Aligning true north.

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Hi, I'm sure it was this forum I saw a video posted of a guy setting up a tripod and using the midday sun while setting his mount plate. Been trying to find it to copy his method when I set my plate and studs in concrete. Anyone remember this or have a link to one they can recommend.

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You can set the iphone compass to display true north rather than magnetic north.  I did that and laid out a sticks as a sightline.  Marked a line across the pier plate and lined them all up.  Your true north is about -1.4deg from magnetic north, (west) (in Exmouth) by the way..

HTH 

Mike

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Slightly off-topic, but it's interesting that the North Magnetic Pole has been shifting at an accelerated rate over the past few years. Only a few decades ago it was in Northern Canada. Now it's actually quite close the the Geographical Pole, and from the UK, magnetic north is now extremely close to true north.

EDIT: Sorry, I was wrong. I've just read that there are actually three, not two north poles! There's the True Geographical North Pole, the North Magnetic Pole and the Geomagnetic North Pole. And they're all different! The North Magnetic Pole is the one which has been moving around, but the Geomagnetic North Pole is the one to which a compass will point and that one is still over North Canada! Very confused now.

Edited by lukebl

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Using the sun

1) put a stick in the ground (.5 to 1m high)

2) make the point of the shadow from the stick

3) come back in an hour or so and mark the point of the shadow

Connect the 2 points and you have an East/West line. Put the south legs of the tripod on this line and the north leg is right where it needs to be.

 

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2 minutes ago, kendg said:

Using the sun

1) put a stick in the ground (.5 to 1m high)

2) make the point of the shadow from the stick

3) come back in an hour or so and mark the point of the shadow

Connect the 2 points and you have an East/West line. Put the south legs of the tripod on this line and the north leg is right where it needs to be.

 

To be successful, the stick must be perfectly plumb with this approach.

Using the same idea, I’ve used a surveyor’s plumb bob (a heavy brass pointy-thingy on a string) to strike a true line on the concrete area where I set up (at least where I would set up if the clouds would leave me alone). 

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Yeah, I need the plumb bob method as my location for the pier is fixed and it's the rotation of the top plate that I need to adjust before setting in concrete. That's why I need the solar noon. If it was just finding North the stick and bisection of the East/West would be adequate. 

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11 hours ago, Merlin66 said:

Anthony,

There a solar tracking site which will accurately show when noon occurs.

https://www.suncalc.org/

Just enter your location.....

thanks, i did find that but ended up on another site and printed out the times for the whole year. just in case i lose internet when i actually get around to doing it. 

http://www.spot-on-sundials.co.uk/calculator.html

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18 hours ago, GoFish said:

To be successful, the stick must be perfectly plumb with this approach.

Using the same idea, I’ve used a surveyor’s plumb bob (a heavy brass pointy-thingy on a string) to strike a true line on the concrete area where I set up (at least where I would set up if the clouds would leave me alone). 

the stick doesnt have to be plumb, just stable, as you're only interested in the very top point of the shadow it casts. 

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16 hours ago, Anthonyexmouth said:

the stick doesnt have to be plumb, just stable, as you're only interested in the very top point of the shadow it casts. 

Agreed. I failed to read your post carefully enough before replying. My apologies!

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