As philaw has already said button compasses prove useful for general direction and should not be expected to provide a means for accurate orientation, but all button compasses are not created equal
A while back I did a quality test of all the button compasses available for a Survival equipment manufacturer
sample of compasses where provided by the following manufacturers
the largest manufacture of button compasses 'Sun' provided:
Item No: 809
Product MiniComp II
Description: Micro Map Compass
Item No: 895-AA
Product 20mm-diameter Compass, Grade AA (.79
Description: Highest-quality (Grade AA) Compass
Item No: 895-A
Product 20mm-diameter Compass, Grade A (.79
Description: Medium-quality (Grade A) Compass
Item No: 895-B
Product 20-mm diameter Compass, Grade B (.79
Description: 20mm-diameter Compass Capsule
Item No: 893-AA
Product 18mm-diameter Compass, Grade AA (.71
Description: 18mm-diameter Compass Capsule
Item No: 893-B
Product 18mm-diameter Compass, Grade B (.71
Description: Economical (Grade B) Compass
Item No: 891-AA
Product Grade AA 14mm Compass
Description: Luminous dial, liquid-filled
Item No: 891-A
Product 14mm-diameter Compass, Grade A (.55
Description: 14mm-diameter Compass Capsule
Item No: 891-B
Product 14mm-diameter Compass, Grade B (.55
Description: Economy (Grade B) Compass
Item No: 889-AA
Product Grade AA 10mm-dia. Compass
Description: Liquid-filled ultra-micro compass
pyser-sgi provided:
the Francis Barker model 1605 NATO button compass, Stock Number 6605 99 522 0223
All brass and glass construction
North and south seeking luminous points
Jewelled sapphire bearing
Niva tipped brass pivot
Silva Sweden AB supplied:
Silva SERE 40 35766-1610 Compass 40 luminous, with lanyard hole
Sunnto supplied:
Suunto Micro Compass (clipper model) Luminous:
A number of compasses where provided for test by other manufacturers but where discarded from test during the initial stages after showing obvious flaws (pointing the wrong way, needle not moving etc)
Tru-Nord compasses where not available for the test
tests where undertaken to assess quality of construction, accuracy, user practicality and durability
the biggest surprise of the tests was the apparent poor quality of the Silva SERE 40 I tested a randomly selected batch of 100 Sliva SERE 40's and found that a +/- 5 degrees inaccuracy from new and 85% developed bubbles at room temperature inside the liquid filled housing during the test, severely reducing the this already substandard accuracy. I have not expected this result due to Silva's reputation for high quality, which it would appear does not extended to its SERE 40
the Sun 891-AA Grade AA 14mm Compass was found to be exceptionally good and of considerably higher quality than the rest of the Sun line. highly accurate and with good luminosity it did not develop any bubbles during the test, though now some 4 years later the one I have in front of me has developed a bubble. very good value for money
The Sun MiniComp II is also worthy of special note as unlike the other compasses in this test it is a full baseplate compass suitable for orienteering, it is not as robust as its counterparts but its accuracy was found to be +/- 2 degrees (though only a very small batch where available during the test) and it developed no bubbles during the test or subsequently. its features make it the most practical micro compass on test and provided that its larger size in comparison to its counterparts is small enough for requirements it should seriously be considered, the only improvement would be if Sun where to use a grade AA compass unit to improve accuracy and provide luminescence
the the Francis Barker model 1605 NATO button compass performed flawlessly as expected, but then one would expect it to at a cost of £20 per compass!!!
it is however not user friendly, it is not liquid filled and although this lends considerably to its robustness it means that the needle is undampend and in order to get an accurate reading it must be placed on a level surface free of movement and allowed to settle.
The outright winner in regards to quality, accuracy, practicality and durability was the Suunto Micro Compass (clipper model Luminous) it is the only compass on test other than the Sun MiniComp to feature a rotational bezel making it highly practical, the luminous markings added to this. is accuracy and build quality where second only to the Francis Barker model 1605 NATO but being liquid filled it was much easier to use. I would use and recommend this model (the civilian version is blue and non luminous, try if you can to obtain the military version)