Go Back   IceInSpace > General Astronomy > General Chat

Reply
 
Thread Tools Rate Thread
  #1  
Old 14-01-2018, 10:56 PM
xelasnave's Avatar
xelasnave
Gravity does not Suck

xelasnave is offline
 
Join Date: Mar 2005
Location: Tabulam
Posts: 16,866
Working out North by the Sun.

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
Reply With Quote
  #2  
Old 15-01-2018, 01:26 AM
billdan's Avatar
billdan (Bill)
Registered User

billdan is offline
 
Join Date: Mar 2012
Location: Narangba, SE QLD
Posts: 1,551
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.
Reply With Quote
  #3  
Old 15-01-2018, 01:40 AM
StuTodd
Registered User

StuTodd is offline
 
Join Date: Dec 2014
Location: Dunedin, New Zealand
Posts: 353
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
Reply With Quote
  #4  
Old 15-01-2018, 02:41 AM
skysurfer's Avatar
skysurfer
Dark sky rules !

skysurfer is offline
 
Join Date: Dec 2011
Location: 52N 6E (EU)
Posts: 1,152
Time zone is incorrect. Local time is shifted several hours.
Attached Thumbnails
Click for full-size image (Screenshot_20180114-173920.jpg)
104.8 KB31 views
Reply With Quote
  #5  
Old 15-01-2018, 09:04 AM
xelasnave's Avatar
xelasnave
Gravity does not Suck

xelasnave is offline
 
Join Date: Mar 2005
Location: Tabulam
Posts: 16,866
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
Reply With Quote
  #6  
Old 15-01-2018, 09:25 AM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
https://www.suncalc.org/#/-38.1667,1...1.15/13:31/1/0

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.
Reply With Quote
  #7  
Old 15-01-2018, 10:21 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney and South Coast NSW
Posts: 5,990
Hi Alex,
Shadow stick method to find True North

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

Martin
Attached Thumbnails
Click for full-size image (A934CDB1-BBAF-4B59-BAD3-C936972E38AB.jpg)
90.9 KB25 views
Reply With Quote
  #8  
Old 15-01-2018, 12:32 PM
ZeroID's Avatar
ZeroID (Brent)
Lost in Space ....

ZeroID is offline
 
Join Date: May 2010
Location: Auckland, NZ
Posts: 4,949
String Plumb bob is best, it HAS to hang vertically.
Reply With Quote
  #9  
Old 15-01-2018, 12:57 PM
xelasnave's Avatar
xelasnave
Gravity does not Suck

xelasnave is offline
 
Join Date: Mar 2005
Location: Tabulam
Posts: 16,866
Quote:
Originally Posted by Merlin66 View Post
https://www.suncalc.org/#/-38.1667,1...1.15/13:31/1/0

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.
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
Reply With Quote
  #10  
Old 15-01-2018, 02:53 PM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
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)....
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:42 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement