Collimating WW2 Binoculars - A Cautionary Tale!

The first encounter I remember with my Uncle's WW2 binoculars, was at a family picnic out at an old RAF Aerodrome in Fradley, near Lichfield. These were always carried in his A35 van, in an open shelf-type compartment on the passenger's side. I never witnessed seeing them in any kind of case or cover.

Collimating WW2 Binoculars - A Cautionary Tale

WW2 Propaganda Poster
The other time I distinctly remember actually using them was at his home, when he asked me if I wanted to: "look at the tanks". With the vivid imagination of a 10 year old spurred on by the association of his time as a Desert Rat, I somehow expected to see something a lot more thrilling than the sewage containers at Bescot.

If you are wondering about these details, then it's because provenance is all with antiques and collectibles and if you know their history you can often come up with a (Sherlock) Holmsean solution to any problem. So, when I was reacquainted with these binoculars some 50 years later, I was disappointed that the view through them was not as clear as I remembered. The images through each side of the binocular were not in line and in fact they were pretty uncomfortable to use for anything more than a few seconds at a time. Seemingly, there was a collimation problem. As I have already collimated a pair of a more modern second-hand, Frank Nipole binoculars (article you can link to below), I did not see this as a problem.

Binocular collimation for WW2 Binoculars

In order to facilitate the collimation and also because it was a good idea anyway, I decided to make a clamp for the binoculars whereby I could attach them to my telescope tripod.

Pallet nomenclature

I used a plank from an untreated pallet and also a 'stringer' from the same.

WW2 Binocular collimation - clamp to tripod

Once the binoculars were mounted in the clamp, I oriented them so that I could look at a television aerial on a house roof some 80 to 100m away. It was very clear that the left-hand image was higher in the eyepiece than that of the right hand image and thus that adjustment was essential. Interestingly enough, vertical collimation errors in binoculars are the hardest for the human eye to compensate.

Collimating binoculars without prism adjustment

Unlike the other pair that I collimated (see above), the objective lenses, could not be easily rotated in their respective cells because of the design.  I was thus faced with the possibility that I would have to resort to prism adjustment and this I was loathe to do! It was at this point that I began to think of provenance, in that these binoculars which had been half way around the World, lugged across the desert and afterwards spend several decades travelling around in various vehicles without any protection before they ended in my mother's wardrobe, were incredibly clean. They also showed no signs of the external damage which are often associated with collimation. This lead me to believe that they had been cleaned on more than one occasion. I therefore wondered what the odds were that the objective lenses had been removed and mistakenly interchanged.

WW2 Binoculars collimation - A cautionary tale

To test my hypothesis I set up the binoculars as if for collimation and initially began slowly to unscrew the left-hand objective lens. The images started to align. So, to determine by how much I would need to rotate the objective lens to achieve aligned images (collimation), I adhered one pieces of electrical tape to the outside rim of the objective lens mount and another piece to the body of the binocular.

Collimating WW2 Binoculars

Collminating WW2 Binoculars - eccentrically mounted objective lens
The collimation was achieved when the lens had been rotated almost three quarters of a turn. I could not imagine how I could fix the objective lens in this position so I continued with the premise that they had been interchanged and therefore, I unscrewed both objectives. On inspection of the inside of both I could see that the left-hand objective was more eccentrically mounted in its holder. The original collimation at time of manufacture had obviously necessitated this adjustment. Therefore, that adjustment meant that once the lens had been incorrectly swapped, the view through the binoculars would be compromised. This would not have mattered if both lenses were concentric in their respective cells.

This is a cautionary tale of a problem which I, with the advantage of having known the history of these binoculars, was able to think through before involving myself in a complicated prism adjustment. Therefore, if you purchase a pair of these World War binoculars, before you resort to any collimation do first consider that, this scenario is probably quite common!

If you have enjoyed this article and found it interesting then share it with your friends on social media or suchlike. Please also feel free to ask questions and or make comments.
Until next time and from a rainy day in Normandie,

Cheers, Andy

© Andy Colley 2018


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