Working out North by the Sun.

[xelasnave]

The Sun should be at true North at noon but my longitude is 151 so should I line up the Sun at 4 minutes past 1 pm tomorrow to get close to North plus a smidgen for the Sun now moving North...or is this approach useless.
Alex

[billdan]

Alex,

You could try this, place a stick in the ground so its vertical and just before noon (or before 1 PM in NSW, due to daylight saving).

Then place a small pebble at the tip of the shadow every 30 secs and where the shadow is at its shortest, draw a line from that pebble to the stick and that is your N-S line.

[StuTodd]

Work out your "solar noon" from https://www.esrl.noaa.gov/gmd/grad/solcalc/ (click a purple "balloon" and an orange one appears which you can move to your location).

Solar noon is the time the sun crosses the meridian as you know, so use a vertical stick in the ground as a gnomon and mark the shadow it casts at the time the website gives solar noon as. That is a perfect north/south line.

Hope that helps.

Stu

[skysurfer]

Time zone is incorrect. Local time is shifted several hours.

[xelasnave]

Thanks most honerable members.
I am trying to align my mount and wish to get as accurate as possible for North.
It seems simple but it is not.
I will set up the mount with no scope and a string line for the shadow which should run down the mount along the rotational line.
Even if my timing is spot on errors of a couple of degrees would be possible.
I only have 15 degrees of sky and no view of CSP so alignment I find difficult.
I hope that being teasonably confident about where North is may help.
Thanks again.
Alex

[Merlin66]

https://www.suncalc.org/#/-38.1667,144.7167,12/2018.01.15/13:31/1/0

This will give you the exact time when the Sun is due North of your location.
I've used similar to set up my NEQ6 mount. The RA axis set level with a spirit level and a Baader film over the finder.
The view of the Sun should be exactly on the finder crosswires at the nominated time.

[Startrek]

Hi Alex,
Shadow stick method to find True North

There are a few similar methods on the internet using the suns shadow

Martin

[ZeroID]

String Plumb bob is best, it HAS to hang vertically.

[xelasnave]

Yes that sounds good.
I may try and use a 150 mm refractor, as I have a sun filter (proper film) for it and an illuminated reticle for cross hairs er wires...Not with it swiched on of course.

And to make the exercise more interesting may try to work out angle of tilt as well. Elevation as I can work out that angle...should be fun to see if I can complete polar align from a noon Sun observation...and it would be so handy as one could get it out of the way before dark...say at a star party it would give you something to do during the day...and given your great link one should be able to do it at other times.

Anyways today was a fail cause I took Dad out for a shop and the time ran out plus I think it had clouded over. Took him to Jkar and he enjoyed it so much.



Alex

[Merlin66]

Hope it helps you....
I used the setting circles on the NEQ6 as a quick check of the declination of the Sun (from the ASV Yearbook)....