where to buy an accurate compass?

[icytailmark]

does anyone know where i can buy a good accurate compass online? My old compass broke i dropped it :( i need a compass that tells me 12.5 degrees east of south for polar alignment just so my mount tracks.

[g__day]

Hmm, Sydney - I'd try the boating stores around Pittwater / Newport if you want a really accurate compass. Not cheap but if you want real accuracy - a maritime graded compass will probably be the best you can buy.

Mind you if you drift align - you don't need the expense of a super accurate compass.

[icytailmark]

i only need a good enough alignment for planet imaging. cheers

[g__day]

Then Dick Smith Electronics or Jaycar will sell a reasonable one for around $40!

[Shark Bait]

I have purchased some navigational items from this business based at Kelvin Grove in Brisbane, QLD.

Scientific Instrument & Optical Sales www.sios.net.au/category/silva-compasses (http://www.sios.net.au/category/silva-compasses)

They sell a good range of silva compasses. I use a Silva Expedition 54/6400 and it is very accurate but not cheap. Sighting compasses make life very easy. It is used for navigating in remote bushlands as well as setting up scopes. It has never let me down and is very accurate. These compasses can also be purchased at camping and disposal stores.

You are probably already aware of this but ensure that it is balanced for the Southern Hemisphere.

[icytailmark]

would any of these compasses be accurate enough?

http://www.raysoutdoors.com.au/online-store/products/Wild-Country-Map-Compass-Large.aspx?pid=241408#Description


http://www.raysoutdoors.com.au/online-store/products/Wild-Country-Lensatic-Compass.aspx?pid=241382#Description

[rainwatcher]

I also use my Silva flat hikers compass. It accurate enough for prep work prior to drift aligning and in most cases when i am just casual viewing with friends and family its fine on its own.

[scagman]

These aren't as cheap as the ones you point out but they are aligned for the sth hemi.
http://www.prospectors.com.au/p-3412-suunto-a-10360cm-sh-field-compass-southern-hemisphere-a10.aspx

[mikerr]

Mark, you might be better off using the Solar Noon plumbob shadow method. Very accurate and no compass needed.
AlsAstroClock can be downloded from the IIS files here....

http://www.iceinspace.com.au/files.html

Als files are toward the bottom of the page.

Yell if you need more info to do this setup using Solar Noon.

Michael.

[CarlJoseph]

:shrug: What does this mean? I thought a magnetic compass pointed north. 180 degrees from that would be south.

Or is there more to it?

[skysurfer]

For polar alignment you don't need a compass at all.
When there is iron and steel in the neighborhood (telescope tube, mount parts) a compass will get inaccurate.
Just use the celestial south pole or the drift method.
I found out myself an alignment method with a bubble level and a wedge with an angle equal to your latitude. No compass, visible north or south pole needed.

http://sky.velp.info/eqmount.php

Or otherwise google for 'polar alignment telescope'.

[Shark Bait]

Hello Afro Man,

The compass needle (or card) needs to be 'balanced' to suit the Northern or Southern Hemisphere. You are right they all point to Magetic North, but if I take my compass too far north of the equator the needle (or card) is going to be out of balance and drag along the compass housing. To complicate it a little more, some specialised compasses like the Silva Expedition models are balanced for magnetic zones within the hemispheres.

[hickny]

Mark,
You could try here http://www.wellingtonsurplus.com.au/listProduct/COMPASSES+-+GPS/EXCALIBUR+ORION+COMPASSES

[naskies]

I just use the compass in my iPhone and handheld GPS for a rough alignment, and drift align using PHD. My phone's accelerometer (gyroscope?) is accurate enough as a bubble level that I usually just drift align azimuth and leave altitude alignment alone between set ups (good enough for 5 min subs at 924 mm on my SLR).

[icytailmark]

just bought a new compass. Decided to buy this one.

http://www.wellingtonsurplus.com.au/showProduct/COMPASSES+-+GPS/SILVA+COMPASSES/SC9020/Silva+Voyager+Compass+-+Model+9020


just hope its accurate enough.

[Shark Bait]

I think the Silva Voyager Model 9020 looks like an excellent compass. Being Silva you can rely on it being a quality product and if you do have any problems Fiskars will honour the warranty. It is far superior to the cheap copies that are little more than toys.

As you can probably tell, I have an interest in navigation. GPS is a great tool, but when the batteries run out nothing beats a map and compass. I would like to know what you think of this particular model when you have had a chance to use it.

Regards,
Stu.

[alocky]

Just saw this thread - I, like almost everyone else in the geological sciences, own a Brunton compass which I've had for over 25 years. Apart from being very accurate sighting/survey compasses, they have an inclinometer built in with a vernier scale. I usually get a rough polar alignment within a couple of degrees with it. However, having seen the price of these things now, you might have to wait for a geologist to die so you can buy one second hand...
http://www.legear.com.au/Brunton-GeoQ-Transit-Waterproof-p/brunton-f-5009.htm

regards,
Andrew.

[Yogie-One]

For what it's worth, I recently bought a Digital Compas (via Ebay) It didn't cost the earth. At a reasonable cost, it digitally displays to fraction of a degree. When I use mine, I view the telescope from a distance, and line North up with a distant object, with the scope in between. Thus no effect from any close metal. I then line the scope up on the distand object, which is North from the scope.

:) :) :) :)

[Irish stargazer]

I picked up a map reading compass from Kathmandu (the shop;)) a few days ago on sale with 50% off. Its quite adequate.

[adman]

Mark - are you always setting up in the same place, or do you move your gear around a lot?

If you are mostly in just one, or a few places, the solar noon/plumbob method works very well, and you know that it is accurate. I never trust compasses unless I know they have been properly calibrated. My father is a sailor, and from memory, he had to draw up tables of his compasses error for each direction. This not only allowed for magnetic deviation that changes at different points on the earths surface, but also for the local magnetic interference of where the compass was sited - he almost exclusively sailed in steel boats, so the interference was significant. I have found compasses that can be up to 10-15 degrees out.

Another method I have used is google maps. Their grid is aligned (I think) true north/south, so you can project that line onto your observing site, and get within a few degrees.

Hope that helps

Adam

[Shark Bait]

In addition to Adam's reply, the following numbers are a rough guide to some minimum working distances to be aware of when using compasses:

Transmission High Tension Lines.....80m
Vehicles.....75m
Railway Lines.....20m
Fencing Wire.....10m
Tools, Shovels (Steel Telescope Mounts ;)).....3m

Every compass, no matter how well made will have an inherant error. Once this error is known, it can be allowed for.

[suma126]

if you have a apple iphone the compass works very well

[mithrandir]

... but is subject to all the same working distance requirements as any other magnetic compass. Walking N/S (line determined by plumb and shadow) in the back yard mine swings up to 10 degrees due to interference. This totally confuses trying to use Sky Safari Pro.

[knowledge]

Hello,

I'm looking to buy a compass to use on a daily basis. What I need is accuracy and affordability. Right now I'm looking at the Silva Polaris. Has any tried this one before, if so, how accurate is it? I really need an accurate compass.

Any suggestions? :question:

Thank you,

-Knowledge

[whzzz28]

http://www.ebay.com.au/itm/Orienteening-Camping-Base-Plate-Compass-Scout-Ruler-D-/290551447100?pt=UK_SportingGoods_Hi kingEquipment_RL&hash=item43a6373e3c

Brought three of these, at $2.50 a pop you cant go wrong!
They work well, so long as they are not too close to metal and must be held level (close to, it has some play) or else the needle hits.

Not the best, but gets me to true south roughly and then i drift align from there - its normally not very far out.

[knowledge]

Thank you for your suggestion.

Has anyone used the brand Silva, or to be more exact, the Silva Polaris?

Here is a link to it:

http://www.llbean.com/llb/shop/63609?page=silva-polaris-compass&catalogId=18

Thanks,

Knowledge

[Shark Bait]

If it is a genuine Silva model you can't really go wrong.

But.....

That site looks like it is American. If it is then you need to make sure that the compass you buy is designed (or balanced) for use in the Southern Hemisphere. If I use a compass setup for Northern Hemisphere in the South, the needle or card will drag or jam against the housing.

Hope this makes sense.

[knowledge]

I don't know too much about compasses... So can you buy a compass that you can use worldwide where ever you go? I plan to use my compass mainly in the US, which is where I am from by the way, and also around the Middle East and that whole part of the world.

Are the Silva compasses that are made in Sweden the good ones? What do you think about this type:

http://www.ebay.com/itm/190686949410?ssPageName=STRK:MEWAX: IT&_trksid=p3984.m1438.l2649

These are from the 1960s I believe.

Thank you,

Knowledge

[Shark Bait]

If you are in the Northern Hemisphere it is the same deal, make sure the compass you buy is balanced for the region you intend to use it.

Silva is a well known brand and their gear is good to excellent depending on how much you wish to spend and what you need the compass to do. There are other Swiss made brands of compass that have excellent reputations as well.

The model in your last post would be a great piece for collectors and probably still works well.

To complicate the issue a little further, if you intend to use your compass in the Middle East it might be better to get a model that can be used worldwide and is not as sensitive to zone changes. These models do exist but they can get quite expensive.

How much do you intend to spend?

[knowledge]

To be honest, I don't intend to spend too much, but I do need it mostly for accuracy and precision. I don't want to spend more than $50 on a compass (maybe sometime in the future I will though) and I think I can get what I need for a lot less than that. The main thing I will be using the compass for is finding directions. If I need to find the direction of Southeast in a particular place, for example, I need it to be extremely accurate in this. Other than that, I do not plan on using it to read maps, etc. I currently use the sun and shadows to guide me in this, but if I can get an accurate compass (after being tested of course) then this will be great and it'll save me much time.

Is there a special name for those that work worldwide?

Thank you :)

Knowledge.

[andyc]

It's hard to suggest what you need without knowing just what you need it for! If you need to take an accurate bearing from your position to a particular object, you should probably go for a sighting compass (for example at Silva here (http://store.silvacompass.com/category/345153/Sighting)). They have a mirror to allow you to sight horizontally while reading the compass dial vertically. This will allow you to take bearings to within a couple of degrees or less, once it is calibrated appropriately. Test your compass by triangulating a known location using a map, also by repeating observations - do all the bearings converge on your location? I have used a similar model to the Silva Ranger CL for fifteen years, using it for geological mapping, geomorphological mapping and navigation on misty mountains in several places in the world. My compass was quite accurate enough to keep me on mountain ridges in mist and snow, or to triangulate outcrops/features of interest onto a 1:25000 map. I can't imagine what you would need to do that would require greater accuracy?

Mine's a Northern Hemisphere model and accurate sighting is more difficult (but not impossible) in the southern hemisphere as you end up having to tilt the housing to allow the needle to swing freely. Tilting the compass back to sight correctly introduces potential error. You shouldn't have such a problem if you're going from the US to the Middle East, using a NH compass - the change in needle tilt will be much less than travelling to the SH. Cairo and Kuwait are roughly the same latitude as Jacksonville FL and New Orleans, so you should have few significant needle tilt problems in much of the Middle East. Hope this helps!