#21  
Old 02-08-2019, 09:44 PM
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Ukastronomer (Jeremy)
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Quote:
Originally Posted by Hemi View Post
Hi Poider,

The compass on my iPhone worked for me, as did the inclinometer.
It got me in the ball park, from there I run the polar alignment routine on the mount to get it spot on (relative to my needs: visual and short exposure imaging). If you have a fully manual mount then Iím not sure. Most posts say getting a dedicated compass to avoid interference. There is a thread on here with instructions on creating sun dial of sorts to get accurate PA using the suns shadow:
http://www.iceinspace.com.au/forum/s...ght=Solar+noon

Regards

Hemi
It's GPS isn't it
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  #22  
Old 02-08-2019, 09:46 PM
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Ukastronomer (Jeremy)
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Magnetic declination, or magnetic variation, is the angle on the horizontal plane between magnetic north (the direction the north end of a magnetized compass needle points, corresponding to the direction of the Earth's magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole). This angle varies depending on position on the Earth's surface and changes over time.
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  #23  
Old 02-08-2019, 11:16 PM
Hemi
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Quote:
Originally Posted by Ukastronomer View Post
It's GPS isn't it
Not really sure....I was just saying how I polar align with the help of my iphone.

I thought iphones used an electronic magnetometer. Some apps use the GPS location to calculate the declination/variation and point to true north.

Switching off the GPS on my iPhone, doesnít affect the compass in any way. Still works as normal.

Hemi
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  #24  
Old 03-08-2019, 05:38 PM
poider (Peter)
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I Have 3 different apps
1, The i phone basic compass, 163 degrees
2, Commander Compass, 170 degrees
3, Astro Locator, 172.56 degrees
Which do i trust? if any and how do I calibrate my phone?
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Old 03-08-2019, 11:12 PM
Hemi
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I just use the basic compass on my iPhone, and manually apply the declination.

Hemi
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  #26  
Old 04-08-2019, 06:59 AM
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Outcast (Carlton)
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Quote:
Originally Posted by poider View Post
I Have 3 different apps
1, The i phone basic compass, 163 degrees
2, Commander Compass, 170 degrees
3, Astro Locator, 172.56 degrees
Which do i trust? if any and how do I calibrate my phone?
This, this in spades....

I use an app on my android phone when setting up my scopes & get wildly varying results!! When setting up my lx90 near enough seems good enough for an az/alt mount but, when setting up my eq mount for either visual or imaging I can be off by as much as 10* & it makes a huge difference to getting alignment & PA!! On occasion I have had frustrating nights both with alignments & then PA, sometimes not really achieving PA at all because the initial setup is too far off!!

I've been considering buying a proper compass but, I saw the post about pavers earlier & am going to investigate that further.
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Old 04-08-2019, 07:54 AM
poider (Peter)
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A normal compass is $120, I will do the sun thing again...... when I see the sun
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  #28  
Old 04-08-2019, 08:17 AM
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A normal compass is $120, I will do the sun thing again...... when I see the sun
Yeah, I can relate... raining up here in FNQ again!! Supposed to be the dry season... & it is, when I'm on shift!!
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  #29  
Old 04-08-2019, 02:18 PM
poider (Peter)
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Low and behold my rookie mistake is there for all to see��took my I pad and I phone outside and they were all the same, so they are all right or all wrong, but according to my solar noon shadow they are all about 10 degrees off. Or my shadow was 10 degrees out
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Old 04-08-2019, 05:35 PM
Startrek (Martin)
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Peter
Shadows donít lie
The Sun is your best friend for finding true south and getting your PA on the starting blocks
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Old 04-08-2019, 05:46 PM
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The Mekon (John Briggs)
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Quote:
Originally Posted by raymo View Post
Sorry Wavey, but magnetic declination is correct, as is magnetic variation. Either term can be used, unless The Oxford Dictionary is mistaken, which
I think unlikely.
raymo
Raymo, I started my seagoing training almost 50 years ago. One of the first things we learned in navigation was compass work, magnetic variation and deviation. When I did my Masters Certificate, it included an extensive course on magnetic compass work, including the correction of compasses. NEVER, had I ever heard of the term "magnetic declination" until I saw it on this forum. I believe the correct term is magnetic variation.

Last edited by The Mekon; 04-08-2019 at 06:38 PM.
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Old 04-08-2019, 06:11 PM
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I find that an arrogant response John. It might depend upon which country
you did your training in. Different countries often use different terms,
especially technical ones.
I was a Flight Engineer back in the day when the crew also included a Navigator and a Wireless Operator, and to alleviate the boredom on long flights I used to chat with the Navigator and watch him work, and he used
the term declination. The U.S., Aus., and the U.K. use different words for quite a few every day items such as the Aussie words guernsey, kerosine, axle,
and muffler, which in the U.K. would be jersey, paraffin, half shaft, and
silencer respectively.
raymo
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  #33  
Old 04-08-2019, 06:44 PM
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The Mekon (John Briggs)
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Raymo, my apologies. No offence was meant. I have edited my post. Had I a ready copy of Nathaniel Bowditch "American Practical Navigator", I would have checked the US usage. But even having read this wonderful book, I cannot remember the term magnetic declination. Perhaps I skipped that bit, as the sections on Loran, Omega, and other navigation systems were more relevant.
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  #34  
Old 04-08-2019, 07:19 PM
poider (Peter)
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I think that I got the term Declination from this website and I also found the 'declination/deviation' of my suburb by looking at the Magnetic Declination Website.
But aside from that if I use the stick and shadow, does that give me the celestial south or do i need to adjust from that shadow for my magnetic deviation/declination?
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  #35  
Old 04-08-2019, 08:38 PM
Startrek (Martin)
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Peter
If you have read my procedure for solar noon meridian true south it specifically mentions the line you mark on the ground is ďTrue SouthĒ and in direct line ( or very close to it ) with the South Celestial Pole ( SCP )
Magnetic Declination or Deviation or what ever you want to call it has nothing to do with my procedure for finding true south. I adopted this procedure from a website link on finding True Celestial South and added some other procedures and information relevant to Astronomers
Cheers
Martin ( Startrek )
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  #36  
Old 04-08-2019, 10:01 PM
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Gentlemen,

After seeing some of the ramblings in this thread about who is or isn't correct about a term..., I'm gonna wade into this somewhat pointless discussion about Magnetic Variation & Declination.

My qualifications:

28 Years as a Royal Australian Naval Officer, Intermediate & Command Navigation Qualified & Command of a Royal Australian Naval Vessel.

Trained in Australia at the RAN School of Navigation, HMAS WATSON..

The Terms Magnetic Variation & Magnetic Declination are, as Raymo states both correct, interchangeable & during my training, within Australia used interchangeably...

To further put rest to the pointless argument I share this:

http://www.ga.gov.au/oracle/geomag/agrfform.jsp

Specifically the section on 'Components of the Magnetic Field'

I'm thinking if it's good enough for GeoScience Australia I suspect it's probably good enough for a bunch of amateurs such as ourselves...

Perhaps we can all now focus on helping Poider (and for that matter me too) with our quest for simple & repeatable setup procedures for alignment in preparation for PA...
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  #37  
Old 05-08-2019, 06:56 AM
poider (Peter)
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My only problem is how to tell if my sun line is correct or if my seven different compasses are correct, I am leaning toward the sun but so far the two sunny days that I have had a chance to do a proper line have been somewhat filled with many other things, the first being not long enough sunlight to accurately mark the line and the second being a friend in need of assistance at the precise time of solar noon. Hopefully will be able to get it done this weekend if there is no cloud, I cannot check my alignment with sigma octans as I cannot see it in my light polluted area, I tried some drift alignment with the moon yesterday but cloud got on the way again
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  #38  
Old 05-08-2019, 07:11 AM
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RB (Andrew)
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Perhaps we can all now focus on helping Poider (and for that matter me too) with our quest for simple & repeatable setup procedures for alignment in preparation for PA...
Well said buddy.

RB

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  #39  
Old 05-08-2019, 07:22 AM
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Sun at local noon is positioned exactly towards North.
Once you have that, just calibrate your compass.
Again, have a look at my post (linked here and earlier in this thread)
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Old 05-08-2019, 08:29 AM
Startrek (Martin)
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Peter
Just to help you out I jumped onto Stellarium and found the exact solar noon times for the following weekend dates in Adelaide -

Saturday 10th August 12hr 21min 4 sec
Sunday 11th August 12hr 20min 58sec

Saturday 17th August 12hr 19min 49sec
Sunday 18th August 12hr 19min 38sec

So if you set up your dowl or rod half an hour before ( make sure itís perfectly at 90 deg NSEW then use your mobile phone to get the exact time, mark your line precisely in the centre of the shadow. The more accurate you can mark it the closer you will be to True south

I set up my HEQ5 mount last week on my line and didnít even have to adjust the Az or Alt bolts my PA was as close as you need it , must have fluked it !!
First time this has ever happened though but my procedure gets you very close
I gave my good Silver compass away to a friend as when I first started a few years ago the compass was giving me different readings each time I used it

Good luck !
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