ICEINSPACE
Most Read Articles
Moon Phase
CURRENT MOON Waxing Gibbous
65.2%
The Sun Now
Time Zones
Sydney
5:39 pm
Perth
3:39 pm
Auckland
7:39 pm
New York*
3:39 am
Paris*
9:39 am
GMT
7:39 am




Go Back   IceInSpace > General Astronomy > General Chat

Reply
 
Thread Tools Rate Thread
  #1  
Old 13-05-2018, 01:53 PM
Allan's Avatar
Allan
Registered User

Allan is offline
 
Join Date: Feb 2013
Location: Newcastle
Posts: 840
Finding the SCP during the day

How do all you imaging types work out were the SCP is during the day? If my magnetic variation is +11 degrees, and I face 169 degrees magnetic, am I facing the SCP?
Reply With Quote
  #2  
Old 13-05-2018, 03:26 PM
leon's Avatar
leon
Registered User

leon is offline
 
Join Date: Apr 2006
Location: ballarat
Posts: 10,384
Allen, i expect if one has a permanent set up that has been aligned to the SCP it will always be aligned to the pole day or night, unless one changes that.

Leon
Reply With Quote
  #3  
Old 13-05-2018, 03:37 PM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
 
Join Date: Aug 2011
Location: Melbourne
Posts: 5,381
You have that correct Allan but one thing you need to be careful of is how accurate your 11º is. I've all buy given up using a compass in parts of my back yard as I am near a tin shed and there is God only knows what under the ground! I have been off as much as 20º and I can watch the needle change magnetic south as a take a step in different directions.

Point is, moving to 169º will probably get you close but you'll definitely need to dial that it at night as it'll either be near perfect or not depending of what is beneath you.
Reply With Quote
  #4  
Old 13-05-2018, 04:03 PM
Kunama (Matt)
MSO Vagrant

Kunama is offline
 
Join Date: Sep 2012
Location: Garran, ACT
Posts: 3,362
Allan, if you're at Coolah tomorrow at 11.57.42 hrs you can hang a plumb bob from the centre of your tripod and the shadow it casts will point to True South, then look up 31.696º and you will be looking at the SCP.....

P.S. sent you an email with the Solar Noon times for your place for the rest of the year
Reply With Quote
  #5  
Old 13-05-2018, 04:54 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Posts: 4,633
Allan your assumptions are correct, but so are the warnings received. Your nice big shed is going to have a good magnetic field effect on a compass, but even a belt buckle can skew the compass. When I was laying out my observatory i used a builders level and compass to paint a point on opposing boundaries where I drove stakes and ran a day glow brickie string line on the 12 degree declination line to mark true north. A laser is a great way to mark straight lines and is unaffected by wind or magnetic fields as long as your sighting location is unaffected. Have fun.

Last edited by glend; 13-05-2018 at 05:10 PM.
Reply With Quote
  #6  
Old 13-05-2018, 05:19 PM
Allan's Avatar
Allan
Registered User

Allan is offline
 
Join Date: Feb 2013
Location: Newcastle
Posts: 840
Quote:
Originally Posted by Atmos View Post
You have that correct Allan but one thing you need to be careful of is how accurate your 11º is. I've all buy given up using a compass in parts of my back yard as I am near a tin shed and there is God only knows what under the ground! I have been off as much as 20º and I can watch the needle change magnetic south as a take a step in different directions.
You need to go into the mining business Colin, it might pay for more astro gear.
Reply With Quote
  #7  
Old 13-05-2018, 05:21 PM
Allan's Avatar
Allan
Registered User

Allan is offline
 
Join Date: Feb 2013
Location: Newcastle
Posts: 840
Quote:
Originally Posted by Kunama View Post
Allan, if you're at Coolah tomorrow at 11.57.42 hrs you can hang a plumb bob from the centre of your tripod and the shadow it casts will point to True South, then look up 31.696º and you will be looking at the SCP.....

P.S. sent you an email with the Solar Noon times for your place for the rest of the year
Thanks Matt, got your email. This is the way to go, and I’ll check how far I’m off with the iPhone compass. I wonder if they get affected by metal in the surrounds, I wouldn’t think so.
Reply With Quote
  #8  
Old 13-05-2018, 05:24 PM
Allan's Avatar
Allan
Registered User

Allan is offline
 
Join Date: Feb 2013
Location: Newcastle
Posts: 840
Quote:
Originally Posted by glend View Post
Allan your assumptions are correct, but so are the warnings received. Your nice big shed is going to have a good magnetic field effect on a compass, but even a belt buckle can skew the compass. When I was laying out my observatory i used a builders level and compass to paint a point on opposing boundaries where I drove stakes and ran a day glow brickie string line on the 12 degree declination line to mark true north. A laser is a great way to mark straight lines and is unaffected by wind or magnetic fields as long as your sighting location is unaffected. Have fun.
I’ll probably use everyone’s info and stake the dobservatory boundary during the day, then check it come night time against the sky.
Reply With Quote
  #9  
Old 13-05-2018, 05:35 PM
lazjen's Avatar
lazjen (Chris)
PI cult member

lazjen is offline
 
Join Date: Dec 2012
Location: Brisbane
Posts: 1,523
Quote:
Originally Posted by Allan View Post
Thanks Matt, got your email. This is the way to go, and I’ll check how far I’m off with the iPhone compass. I wonder if they get affected by metal in the surrounds, I wouldn’t think so.
If it's anything like the Samsung phones for sensitivity - then it most certainly will be affected. I generally use it to get in the general area, then do the aligning at night via other methods.
Reply With Quote
  #10  
Old 13-05-2018, 09:47 PM
LewisM's Avatar
LewisM
Novichok test rabbit

LewisM is offline
 
Join Date: Aug 2012
Location: Somewhere in the cosmos...
Posts: 7,943
Quote:
Originally Posted by Allan View Post
How do all you imaging types work out were the SCP is during the day? If my magnetic variation is +11 degrees, and I face 169 degrees magnetic, am I facing the SCP?
PPL Navigation

Borrow an INS / GPS from work. I am sure they'll let you
Reply With Quote
  #11  
Old 13-05-2018, 11:35 PM
jimmyh1555 (James)
jimmyh1555

jimmyh1555 is offline
 
Join Date: Jun 2017
Location: George Town TAS
Posts: 129
You must specify whether it is variation EAST or WEST. The mariners adage is "Variation East, steer least, variation West, steer best."
ie if you want to point to 180 degrees, then turn compass needle to point to 169 degrees. If your variation is 11 degrees West, then to point due south, get the needle to point to 191 degrees.
Easy, EH!
Reply With Quote
  #12  
Old 15-05-2018, 11:05 AM
Wavytone
BigBanger

Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 3,026
Straight answer: In Newcastle, yes.
Reply With Quote
  #13  
Old 15-05-2018, 11:30 AM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Posts: 4,633
Actually, Magnetic declination in Newcastle, Australia is*+12.41°*

Allan, at your sight near Coolah, well actually at the Black Stump near the turn off, it is:



Latitude: 31° 44' 44.5" S
Longitude: 149° 42' 21.2" E
Magnetic declination: +11° 19'*
Declination is*POSITIVE (EAST)
Inclination: 62° 28'*
Magnetic field strength: 56128.0 nT

So I would suggest using +11.2 degrees.

The source of this information is:
http://www.magnetic-declination.com/...le/122944.html

Just drag the map over to Coolah (Black Stump) and click on that spot on the map.
A box will appear with the above information enclosed.

I tried to pick out your driveway on the map and the website said +11.17 degrees if you want that level of precision.

Last edited by glend; 15-05-2018 at 11:43 AM.
Reply With Quote
  #14  
Old 15-05-2018, 06:38 PM
billdan's Avatar
billdan (Bill)
Registered User

billdan is offline
 
Join Date: Mar 2012
Location: Narangba, SE QLD
Posts: 1,026
The Azimuth bolts on most mounts give you +/- 3 degrees leeway, so if you are within that range during the day, you can fine tune at night.
Reply With Quote
  #15  
Old 15-05-2018, 07:55 PM
The Mekon's Avatar
The Mekon (John B)
Registered User

The Mekon is offline
 
Join Date: Jul 2007
Location: Bowral NSW
Posts: 627
Quote:
Quote:
Allan, if you're at Coolah tomorrow at 11.57.42 hrs you can hang a plumb bob from the centre of your tripod and the shadow it casts will point to True South, then look up 31.696º and you will be looking at the SCP.....
Matt, I love you for this. So many times I have seen on this forum posts about magnetic variation (mariners never use the term "declination") and calculating this to find true south.
Your method is the correct way to plot a true N/S line. Problem is that most people do not know how to find the exact time of the sun's meridian passage. Perhaps Allan was shown this early in his navigation training, but other matters soon overtook it in importance. Maybe one day I will do a post of how to find this time - it may be easily available for any location on the net these days - I would not know.
Reply With Quote
  #16  
Old 15-05-2018, 10:02 PM
Wavytone
BigBanger

Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 3,026
Local solar noon: look it up here:
http://www.spot-on-sundials.co.uk/calculator.html

Hang a plumb-bob - (a rock on a string will do) - the shadow points due north-south at that time. It will be more accurate than any magnetic compass and should get you within half a degree.

When setting up my mount, using a compass app in my iPhone and just eyeballing the offset by standing north of my mount and noting some distant mark at a bearing of 169 degrees, typically results in an initial azimuth error less than +/- 2 degrees. Sometimes I'll make the effort to get it below a degree using the dec setting circles.

And yes JB is right - the correct term is magnetic variation - not declination.

Unless theres something steel the size of a car within 15 metres you can forget local influences.

Last edited by Wavytone; 16-05-2018 at 10:04 PM.
Reply With Quote
  #17  
Old 16-05-2018, 08:15 AM
Kunama (Matt)
MSO Vagrant

Kunama is offline
 
Join Date: Sep 2012
Location: Garran, ACT
Posts: 3,362
Quote:
Originally Posted by The Mekon View Post
Matt, I love you for this. So many times I have seen on this forum posts about magnetic variation (mariners never use the term "declination") and calculating this to find true south.
Your method is the correct way to plot a true N/S line. Problem is that most people do not know how to find the exact time of the sun's meridian passage. Perhaps Allan was shown this early in his navigation training, but other matters soon overtook it in importance. Maybe one day I will do a post of how to find this time - it may be easily available for any location on the net these days - I would not know.

John, I cheated and went to an online calculator.... in my defence I lost my Nautical Almanac three decades ago, can't remember the Arc to Time conversions and no longer own a sextant...... lucky for me though, I live in Canberra where the Solar Noon and Local Time are almost coincident, for example, tomorrow the Solar Noon here is at 1200hrs..
Reply With Quote
  #18  
Old 16-05-2018, 10:02 PM
miker
Registered User

miker is offline
 
Join Date: Aug 2008
Location: Australia
Posts: 45
Als Astro Clock.
http://www.iceinspace.com.au/downloa...75375730146e40

This will show you Solar time.

Michael
Reply With Quote
  #19  
Old 16-05-2018, 10:06 PM
Wavytone
BigBanger

Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 3,026
Only for Windows users. Not OSX, iOS, Linux or Android.

And sorry but I don't run windows apps from sources I can't trust. For all I know it may be little more than a .BAT file containing DEL C:\*.* /R
Reply With Quote
  #20  
Old 17-05-2018, 05:46 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 10,543
Hi Allan

I'm a little late to the discussion on this topic, but here is a link to how I manage to get very close to the SCP in the daytime.

http://www.iceinspace.com.au/forum/s...ad.php?t=14036

The details are spread over a few posts, Msg #1 and #29 in particular.

Cheers

Dennis
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 05:39 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Advertisement
FLI Cameras and Imaging Accessories
Advertisement
Lunatico Astronomical
Advertisement
SkyWatcher WiFi Adaptor
Advertisement
SkyWatcher 2018 Catalogue
Advertisement
Interest Free Finance
Advertisement
Bintel
Advertisement
Atik Horizon
Advertisement
OzScopes Authorised Dealer
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement