Finding the SCP during the day

[Allan]

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?

[leon]

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

[Atmos]

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.

[Kunama]

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..... :2thumbs:

P.S. sent you an email with the Solar Noon times for your place for the rest of the year :lol:

[glend]

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.

[Allan]

You need to go into the mining business Colin, it might pay for more astro gear.

[Allan]

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.

[Allan]

I’ll probably use everyone’s info and stake the dobservatory boundary during the day, then check it come night time against the sky.

[lazjen]

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.

[LewisM]

PPL Navigation :lol:

Borrow an INS / GPS from work. I am sure they'll let you :P

[jimmyh1555]

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.:D
Easy, EH!

[Wavytone]

Straight answer: In Newcastle, yes.

[glend]

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/Australia/Newcastle/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.

[billdan]

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.

[The Mekon]

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.

[Wavytone]

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.

[Kunama]

:lol: 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...... :thumbsup: 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..

[miker]

Als Astro Clock.
http://www.iceinspace.com.au/download.php?071cb351c86bc34c9b7537 5730146e40

This will show you Solar time.

Michael

[Wavytone]

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

[Dennis]

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/showthread.php?t=14036

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

Cheers

Dennis

[DRCORTEX]

This is one nifty trick. tried it today with solar time and correct declination. Works a treat. I was quite stunned by how far I was originally out using a compass.

Thanks!

DOC

[Startrek]

Here’s my method , never fails and gets you fairly close
Solar Noon ( shadow stick method )
Once your tripod is aligned and mount is fitted and set in home position, just set your altitude on the mount to your local latitude