Cammenga Lensatic Compass

Summary

Well-made, but less than ideal for non-military users.

The U.S. M-1950 dry lensatic compass currently made by Cammenga gets a lot of good press for being tough, but it's only 'tougher' than most liquid-damped 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 — a 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 degree scale is given second place on the dial. As a result, the degree scale is only marked in large five-degree increments — 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 twice with your eye to get a (theoretical) reading of 1.25 degrees, 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. 

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 its 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 the floating dial in 'six seconds or less'. Fine, except that in comparison, my liquid damped orienteering compass with 'global needle' settles in less than two seconds, and stays rock-steady.  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 M-1950 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 M-1950 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 tritium sighting is a great option for low light and the occasional emergency night hike, and should be available on other compass models here in the states (outside North America, anyone can buy a Silva of Sweden 4b or 54b Expedition military compass with beta, or tritium lighting).  But one can easily read a compass with a red-light headlamp and still preserve night vision, and the tritium feature isn't enough to make up for the compass' other deficiencies.  

In summary, the M-1950 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.  

Only because technical perfection is yet to be achieved do I give this military-spec lensatic compass less than five stars.

As another reviewer has mentioned, its case is as sturdy as can be imagined for a hand-held compass, being machined of aluminum to house the compass workings. Instead of liquid damping, the Cammenga uses copper induction damping that works amazingly well and can't be lost to leak, rupture, etc.--as happened to my old Silva Ranger that I bought this to replace.

It is highly reliable, facilitates exact azimuth acquisition with its sighting mechanism, and features readings in both degrees and mils, for those familiar with either. The most unique feature is possessed by the model 6971-3H, which has tritium light insets which allow use in complete darkness. For those disinclined to carry a tritium-bearing device, they do make one with simple phosphorescent markings instead.

Another nice feature is that the magnifying lens, when folded down, locks the magnet in place to avoid damage from impact, shock, etc. The compass also comes with a nylon carry case, a lanyard, and belt clip for the case, as well as a brief instruction manual written in very direct military style.

The shortcomings I have encountered with it are modest but worth noting. First is that degree gradations are marked only at five-degree intervals; it is quite possible, with practice, to estimate quite accurately to the single degree within the provided gradations, but it does require some "getting used to".

The second quibble is that the scale markings along the straight edge available when the compass is completely open are suitable for 1:50,000 scale markings, but some of the markings (specifically, those for 2000 and 4000 m) aren't marked so as to quickly distinguish them from neighboring marks.

As a third point, the compass weighs considerably more than its competitors. For the gram-counters out there, this is NOT their compass of choice. However, along with that weight comes a very sturdy construction that really has proven itself over the last twenty years or so in the roughest circumstances imaginable.

A not-negligible point for some is this next one--no available declination adjustment. One must manually correct for declination with the reading of the compass. While not difficult for an experienced user, someone who is used to setting declination and forgetting it thereafter will have to be reminded occasionally to make the proper adjustment in sighting.

And, finally, it has no mirror. Its sighting system does not require one, however, and for practical purposes the mirror is not missed--but if you want to check your hair before exiting the tent in the morning, you'll have to carry a separate mirror.