User Review: Cammenga Compass (U.S. M-1950)
Source: bought it new
Well-made, but less than ideal for non-military users.
- Air-filled compass housing can't develop a bubble
- Excellent manufacturing and assembly quality
- Deep-well compass housing
- Mediocre accuracy
- Mediocre shock resistance
- Degree scale in 5-degree increments only
- Can fog over in certain conditions
- Wobbly, slow-to-settle compass dial
The U.S. M1950 dry lensatic compass currently made by Cammenga gets a lot of good press for being tough, but it's only 'tougher' than most liquid-filled baseplate compasses in that it can't ever develop an air bubble in the housing, since it doesn't use liquid to dampen the dial.
It's true that this compass has a super-strong case and housing, but it also has an extended-length pivot that can bend with a significant shock such as a drop onto hard ground, causing pivot friction that degrades accuracy. Note the official military 'shock' test — an easy 'drop' test of 90 cm (3 feet) onto a plywood table covered with a 10 cm (4-inch) layer of plastic-covered sand.
This compass is often praised for its superior accuracy over most baseplate style compass designs in shooting an azimuth (taking a bearing) to an objective or landmark. Let's examine that.
The compass dial is in both mils and degrees, and as the military uses mils, the mils scale is placed on the outside circumference of the dial, while the degree scale is in red ink and relegated to second place on the inside, with only five-degree increments or markings — a dial you'd expect on a $10 compass, not one costing $50 or more.
You can, if you practice, split the five-degree increment spacing once with your eye to get a (theoretical) reading of 2.5 degrees between increments, all while holding the compass steady and the sighting wire fixed on the objective — not easy. Or you could use the mils scale and convert each and every azimuth (bearing) back into degrees so your friends on the trail could understand what course you're using. But why bother, when there are other compasses out there with dials that can be easily interpolated to one-degree or less without computations?
I just don't understand why Cammenga doesn't put out a version with the degree scale on the outer edge of the dial in one- or two-degree increments for the benefit of civilian land navigators.
Then there is the issue of inherent accuracy. Brand-new, the G.I. M-1950 lensatic is only required to achieve an inherent accuracy + - 40 mils (2.25 degrees) from actual azimuth under milspec requirements. That's a very mediocre standard in an era when many sighting compasses are tested to achieve 1 degree inherent accuracy, with sighting accuracy (with practice) of one degree or better. Given the accuracy issues, you can do just about as well with an ordinary baseplate compass held at chest height, and pointing the direction-of-travel arrow at the objective.
That dry card housing can't ever form a bubble or leak. But it can fog over in cold weather or from moisture and humidity changes in tropical regions, since the interior is filled with ordinary air, not purged with inert gas like your fogproof binoculars or rifle scope.
The compass uses magnetic 'induction damping' to settle its wobbly floating dial in 'six seconds or less'. Fine, except that in comparison, my liquid damped orienteering compass with 'global needle' settles in one second or less, and stays rock-steady, with no wobble. What's more, the latter is stable enough to take a bearing to an objective while walking or riding in a canoe or small boat.
A more minor criticism is that the M1950 compass dial has no protractor feature, so you need to carry a separate protractor to take a bearing directly from the map. It has no romer scales, and only one 1:50,000 metric scale, which isn't much use for USGS 1:24,000 topos. It also has no adjustable declination feature for relating all compass headings to true north. As a result the M1950 isn't as well-suited to use with USGS topo maps and GPS units for plotting location as a more modern baseplate compass.
The compass itself is built with attention to detail and all parts on my example were well-fitted with no signs of manufacturing or assembly defects. Cammenga does an excellent job on meeting milspec standards. The luminous lighting on the standard model is excellent, once charged with a flashlight, but if you have a flashlight anyway, the luminous feature isn't really necessary.
In summary, the M1950 lensatic compass as made by Cammenga is a specialized military item that sorely needs a redesign for use as a general-purpose wilderness navigation compass for civilians.