Compass

[poider]

So when going for polar alignment with a compass, is a compass app on a smart phone accurate enough or should I just go and buy a compass, I can not see the octans stars from my light polluted location?

[Ukastronomer]

Personally I think the multi billion $ GPS system may be more accurate than a $10 compass

[xelasnave]

I tried out a compass app today..CSP was about 20 degrees away from where I have placed it with star trails...so not impressed..if you can take a long exposure so you get star trails and that gives one a pretty good idea. CSP is what all those semi circles the star make have as their center as we all know.
Before I got pole master I would site the camera (with scope preferably) to see the same as the view thru the polar scopeduring the day so later with star trails I would get pretty decent alignment.
Alex

[xelasnave]

I am going out right now to see how a new planetarium app may assist to get a ruff idea...I am working out which trees need to come down...well confirming my selection.
Alex

[xelasnave]

Well that didn't go well...pointed at Jupiter and at first it was seemingly spot on ..then tried to find CSP...didn't seem to be marked on the app..but when I tried it on Jupiter again I had to point 15 degrees away from it for it to show on the app.
I like the star trails still.
Alex

[Hemi]

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 I’m 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/showthread.php?t=175771&highlight=Solar+noon

Regards

Hemi

[Hemi]

Hi Alex, I’m not sure what app your using, but the gyrometer in your device might need recalibrating. I use sky safari and find its pretty accurate.

Cheers

Hemi

[xelasnave]

Thanks Hemi. I expect you may be correct...I was not prepared to get cold sorting it out ...I expect the compass problem is for the same reason. I was not happy last night ...it was cloudy at Sunset with some sprinkles so being still cloudy around eight I lite a fire to burn off some excess wood. I went out a little time before my post to check the fire after a rain front passed ..I wanted to make sure it was out before I went to bed...and wouldn't you know it..the sky was nice and clear..and I had not set up.
The phone I have is only a couple of days old and we are still getting to know each other.
Mind you what I have noticed is the camera is , by my phone standards, extraordinary.
Alex

[Startrek]

Solar noon meridian method gets me under a degree
All you need is a timber dowel , some string , a good float level and a sunny day

I gave my Silver compass away to a bushwalking friend as it was a waste of time , needle keeps moving as there’s to much iron around and forget using your iPhone it’s way off

Let me know if you want a procedure

[Startrek]

The good old Sun never fails spot on every time !!

[poider]

Thank you startrek I have seen your tutorial, a friend told me to use the sun and a stick, I did and it was fairly close, but I now want to do a permanent mark of some sort and only have a grassy backyard, I will try again on the weekend if the sun allows me to, last weekend I had about two seconds of sunlight within a minute of the high noon so wasn’t as spot on as I wanted

[Wavytone]

The apps in iPhones are ok if they are calibrated.

No idea about androids...

[bojan]

This is how I do it
http://www.iceinspace.com.au/forum/showpost.php?p=1356126&postcount=23

[poider]

If I stand facing south my compass reading is 180 degrees, my magnetic declination is 7.5 east positive, does this mean that if I stand with my compass reading 172.5 I will be facing true south

[bojan]

Your true south will be 7.56° to the East (left) side of where magnetic needle points at.

Mine (Melbourne) is ~11°.. see picture (http://www.iceinspace.com.au/forum/attachment_browse.php?a=223392) and/or map: https://www.victorianseekersclub.org.au/navigation

[Startrek]

Peter
If your plonking your tripod down on grass I would recommend to find 3 pavers or bricks and set them into the ground reasonably level on some gravel or blue metal so your tripod legs have something solid to sit on otherwise your tripod and mount will sink at various times according to the weather especially in wet weather
In regard to your true south line ( SCP ) just buy a 300 x 300 or 450 x 450 concrete pad from Bunnings and sit it level on the ground centred below your tripod and you can use the solar noon meridian method to score a permanent line on it for your true south direction
You can mow over the bricks and pavers if they installed level just below the grass finished cut level
Get the idea ?

[poider]

Thank you all for your assistance, I have been thinking of putting down three pavers for some time now so I am on the right track

[Wavytone]

By the way please use the correct term - which is "magnetic variation".

Declination refers to the position (geocentric latitude) of astronomical objects, it has nothing to do with magnetism.

[gjr80]

Hmm, maybe a few others (https://www.usgs.gov/faqs/what-declination?qt-news_science_products=0#qt-news_science_products) need educating too.....

Gary

[raymo]

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

[Ukastronomer]

It's GPS isn't it :)

[Ukastronomer]

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.

[Hemi]

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, doesn’t affect the compass in any way. Still works as normal.

Hemi

[poider]

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?

[Hemi]

I just use the basic compass on my iPhone, and manually apply the declination.

Hemi

[Outcast]

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.

[poider]

A normal compass is $120, I will do the sun thing again...... when I see the sun

[Outcast]

Yeah, I can relate... raining up here in FNQ again!! Supposed to be the dry season... & it is, when I'm on shift!!

[poider]

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

[Startrek]

Peter
Shadows don’t lie
The Sun is your best friend for finding true south and getting your PA on the starting blocks

[The Mekon]

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.

[raymo]

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

[The Mekon]

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.

[poider]

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?

[Startrek]

Peter
If you have read my procedure for solar noon meridian true south it specifically mentions the line you mark on the ground is “True South” 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 )

[Outcast]

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...

[poider]

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

[RB]

Well said buddy.

RB

:thumbsup:

[bojan]

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 (http://www.iceinspace.com.au/forum/showpost.php?p=1356126&postcount=23) and earlier in this thread)

[Startrek]

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 it’s 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 didn’t 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 !

[Merlin66]

Guys,
I find the SunCalc App to be excellent for meridian alignment.
https://www.suncalc.org/#/-38.1667,144.7167,12/2018.01.15/13:31/1/0
Just enter your location (You'll get that from GPS or Google maps) and the date.
Recommended.
(I set up my portable HEQ5 for solar observing by using the aligned finder (fitted with a solar filter). The top of the EQ head is set horizontal using a spirit level, counterweights down. Set the Dec using the circles to the solar Dec (as given) and check the solar image is visible in the finder...tweak as necessary. Use the alt/az adjusting bolts to bring the solar image exactly in the middle of the cross wires at the specified time. Perfect meridian alignment. Sound complex but like many things in life - the first time is the most difficult - after that it's a piece of cake! I've now marked the tripod feet position on the deck and find that works now 99% of the time.)
Hope that helps.

[raymo]

No probs John, as the youngsters would say these days.
raymo

[poider]

Quick update I used the stick and the sun, marked out my line and placed my pavers, I only need put my legs in the paver holes and i am near spot on each time, but now my tripod has broken and I am using my camera tripod, a bit shorter but I can still get pretty close, i can find the sigma octans most night in my alignment view finder, but now I am going up to Uluru for a week and need to have a quick way to find the SCP from there. I will let you all know how I go.
From home I can get some decent shots at up to 5 minutes with the camera, no telescope on a good day with the star adventurer.
Thank you all for your help, It has been a while since posting as I don't get out as much as I should, I have bad lungs and cannot go out when it is too cold or when the neighbors are burning bad stuff in their combustion heaters, but I do get out occasionally.

[Startrek]

Peter,
The solar noon shadow stick method is bullet proof , the human race has been using the suns shadow for thousands of years for time measurement, constructing monuments and buildings , cultural and spiritual reasons and even Indiana Jones used it in Raiders of the lost Ark ( pardon the joke )
The Compass has its use but not ideal for aligning tripods to true south
Glad it has worked out for you
The more accurate you are with your shadow stick set up and true south line , the more accurate and closer you will be to true south and resultant polar alignment
Cheers
Martin

[AdamJL]

Out in the field, which is where I do all of my shooting (not possible at home), I just use a rough alignment with a good compass, then dial it in with the digital.
Since I only shoot in 3 locations, I know exactly where to point my mount. Everytime I fire up the PoleMaster, Sigma Octantis says hello to me at first attempt in the image.

[Hemi]

I think the solar noon method is fine, but for me it’s not that useful as you can only use it at noon. I normally get to a dark site late afternoon. I also find it a bit of a hassle with the sticks and string and all.
There are a number of these threads and I’m flummoxed why people struggle with compasses (iPhone or regular). It just has to get you in the ball park, after which you have to use another method anyway (drift, aspa, sharpcap etc).

I use my iPhone compass and a small orienteering compass. Then ASPA or PemPro, session dependent.

Best

[Hemi]

Thanks Merlin,

Missed your post...very neat method, will try this.

[astro744]

Thousands of years ago there were no apps to help you find solar noon, (as your method attached to the other thread suggests). You need to determine solar noon another way first and you can do this simultaneously as solar noon will be when the sun is at its highest point and therefore any vertical stick shadow will be the shortest length. The shadow length will vary depending on where you are located in latitude and the current season.

Place the stick as described over a concrete slab and mark the end of the shadow with a dot from morning to evening every hour to every few minutes as you approach solar noon and afterward. When you connect to dots you will get a curved line. Solar noon occurred when the radial (shadow length) is at its shortest. You can confirm this by placing a dot at precise solar noon that you obtained the time using your app but note this was not an option thousands of years ago.

As for the various shadow methods used in the movies all I can say is you must be very lucky to be at the right place at the right time of day and the right time of year and for it to be sunny and not overcast. The best flawed example I remember is in National Treasure when the sun cast a shadow on at a particular spot to reveal a clue. What a fluke to be there at the precise moment the clue was hidden even when they thought they were smart enough to take daylight savings into account. (Still enjoyable movie though!).

[poider]

Which Multi million dollar GPS?
I have used 5 apps on my phone
and 5 different resources on the net
Pro compass, Commander compass, I phone compass, Astro locator and polar alignment pro for the I phone apps
and on the net magnetic declination .com, google earth, google maps, gps coordinates and find my gps
The results varied five were one coordinate and five were another
these are relatively close but are 35km apart
So maybe the multi billion dollar Gps System need to be re callibrated

[mura_gadi]

Not for finding celestial south but...

On my SW goto, I used the pavers and made a mark on the pavers for an inverted "L" pole. I return the scope to the same leg position and check level on the stand.

Then use the pole on the paver mark, move the scope till the edge of the scope hits the pole, I know I'm pointing north, move the scope up till it hits the "L" bar and I know I am level.

Saves a bit of time in the backyard over compass and a spirit level, well, once you've setup up the pole anyway.



Steve

[poider]

I have three pavers in my back yard now with holes... the leading paver is south I was doing well but have now bought a new stronger 'surveyors' tripod, tonight I will check my alignments and make sure I can repeat it in the field.
I went to Uluru to get some really dark skies and try for some really good shots, Uluru recorded its highest rainfall in many years whilst were were there, so now I am booked for the Flinders Ranges to bring some rain to the dry parts of the state.