Fixing World War 2 Binoculars - Perfect Optics From the Past

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, England. 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.

The second 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 my uncle's time as a 'Desert Rat', I somehow expected to see something a lot more thrilling than the town sewage tanks/containers, half a mile away!

Fast forward a few decades, to my mother turning out her whole wardrobe to look for a particular wrap to match my wife's dress and out tumbled my late uncle's WWII binoculars. They were a little battered, still without a case but serviceable despite being 8th Army issue and having been lugged across the desert sands. I wondered how good they would be for astronomy, as often there are objects I'd like to view without getting out the whole telescope.  On trying them out, 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 and tiring to use, for after a few seconds viewing, I found my eyes straining to compensate for the misalignment.  However, because of the quality and the relatively simple construction these binoculars, unlike many of their modern counterparts can be fixed. So I set out to fix them.

Step 1: 4 Good Reasons to Fix - Build Quality of Optics and Materials

'I have examined modern fully-coated binoculars of inferior optical design and quality that could not hold a candle to some Zeiss units made in the 1930s.' J.W. Seyfried, author

The army issue binoculars of this period, in almost every case, use uncoated optics. Nowadays all optics are given several coatings to improve image quality. However, from my initial views through these binoculars, I can testify that the image quality is sharp across almost all the field of view and fringing is undetectable. The reason for this is the basic optical quality of the glass used prior to WWII. 

The Bakelite eyecups, which have an integral threaded brass bush within them, are an example of good engineering practice. Nowadays binoculars in this price range and above have plastic threading, which is prone to stripping if not correctly engaged.

Another bonus I have discovered, is the individual focus of the binoculars, a design used prior and during the war due to ease of manufacture, robustness and waterproofing. Central focus was a selling point of the post war period but it brought with it several problems, not the least of which was it being the first component to fail, particularly, in my experience, on compact binoculars. I remember trying a pair of pricey, secondhand binoculars with central focusing in a Birmingham camera shop only to find that the focusing linkage was broken!

Ordinarily cheap binoculars do not have good eye relief, aka the distance from the eyepiece to the eye. This is because manufactures focus on magnification ("power") as a major selling point. Due to the optics of the 6 x 30, eye relief is so good that the binoculars can be used even when wearing spectacles. Poor eye relief means that the binoculars must be held right up to the eye which can become very uncomfortable for stargazing or bird watching.

Step 2: Starting With Some Background Research

Despite their rough and ready appearance, WWII Binocular optics were actually manufactured to a very high standard. The companies who made them saved money on the casings and strappings but were required by the Armed Forces to furnish precision lenses and prisms. Thus in WW2 binoculars you are getting a usable quality optic (of its time) for very little money.

Many binoculars were actually given loaned and/or purchased from civilians, thus there were many variations in dates and makes to the standard army issue. In Britain all items were required to be marked with a broad arrow or heraldic 'pheon' by the Ministry of Supply, this to denote government ownership. In the case of my uncle's binoculars there is no such markings but then neither is there a manufacturer's mark either. In effect, as you can see in the photo above, the company's name has been very obviously scratched off and obliterated. Similarly, I'm guessing, has the government mark! In very many cases these useful, precision instruments were repatriated with their war-time users. The not so quality ones being no doubt left in the desert.

Despite the missing markings and having researched and viewed a whole panoply of fabulous vintage binoculars from around the World, my guess is these are Kershaw of Leeds standard issue binoculars 6 x 30 known as the No 2 MkII. However, as the optical information is positioned differently to that of all the rest I have seen (below rather than above the removed manufacturer's mark) I am still open to suggestions.

Also included above is a photo of a British Intelligence Officer with his Kershaw's No2 MkII and a WW2 Poster asking for the loan of binoculars to the Navy.

Step 3: Safety First - Making a Clamp

In order to easily and safely diagnose the problem, I decided to make a clamp for the binoculars whereby I could attach them to my telescope tripod. This was constructed from some pallet wood planks, rough and ready but solid.

Step 4: Optical Alignment

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.

Step 5: Collimation?

Unlike a modern pair that I had collimated (see https://www.instructables.com/Binocular-Collimation-Quick-and-Easy-Method-Withou/) 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, cleaned and mistakenly interchanged.

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 piece of electrical tape to the outside rim of the objective lens mount and another piece to the body of the binocular.

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.

Step 6: Elementary, Sherlock

This whole exercise taught me a lot about the diagnosis of problems and how even an initial quick glance can tell so much i.e. the case of the missing screws as seen in the photos above.

There are more things that can be done to these binoculars even though they are now quite usable, I believe they can be even better. In writing this I had occasion to get out my magnifying glass and go over them again only to find a minute screw in the each objective lens housing (first two photos above). The screw is missing on the right hand side and the left is hidden by a black wax plug, this leads me to believe that the binoculars have been stripped down completely and reassembled (carelessly) at some time.

Step 7: Buying to Fix - a Handy Guide

Fixing these binoculars meant I did quite a bit of research on provenance and problems, so I thought I'd share these ideas to help in locating a fine pair for yourself.

Standard issue WW2 binoculars can be purchased for as little as single figures and many of the problems/injuries they have incurred over time are repairable. However, I would always consider the price in light of any potential labour involved and maybe pay a little more for a better pair. There were several manufacturers who made military binoculars and it is a good idea to view as many pairs as possible and get a feel for the current market prices and values. This said, it can be very satisfying to give these great pieces of optical engineering a second life.

MOULD - in particular if the binoculars do not include a case, you should be aware of the fact that mould spores can enter and begin to colonise a lens when it has been kept in damp conditions. There are things you can do to control the spread of this, such as the use of UV light but it is something you should be aware of and decide if the price has been adjusted accordingly. HEAVY MOULD however should be avoided. Colonies of mould can actually etch the glass of the lens, causing damage which will need expert and costly repair.

DAMAGED LENS ELEMENTS - this occurs with the age of the instrument, the cement joining two lens elements deteriorates. However, solutions exist whereby the lens elements can be separated, cleaned and re-glued. Again consider this in relation to the asking price.

OUTGASSING - the oil and grease within the casing of the binoculars can sometimes deteriorate with age causing a process known as outgassing which can leave a deposit or film on the optics and housing. This will show up as a misting or hazing when the binocular is used, resulting in a loss of contrast. It is often difficult and costly to repair.

CRACKED OR BROKEN LENSES OR PRISMS - I would only consider these for spares and repairs. It is sometimes both practical and certainly economical to buy a couple of damaged pairs and make one good serviceable one!

GENERAL APPEARANCE & MECHANICAL FUNCTION - Given that most of these binoculars were manufactured for years of War Service, envisaging various climates and environments they are built for robustness and not looks. Do not be put off purchasing due to a shabby or paint-chipped exterior. This is to be expected as these items have quite literally 'been through the wars'. However, there are certain elements which are crucial if you are going to want to use these in the field. Here is a short checklist of what I look for:

Central Hinge is not loose,

Focussing Mechanism is smooth,

Denting to body is superficial and nothing that could indicate interior damage or initiate further problems.

Cleanliness of Optics - although a certain amount of dust and grime is to be expected and can with care be removed, highly contaminated lenses may mean poor storage and are perhaps indicative of further and more serious neglect.

Indications of Cleaning - be aware that an inexperienced seller may have 'cleaned' the optics prior to offering for sale. Unless done with care, this process can have caused more harm than good, resulting in scratched or damaged optics. In effect there is a school of thought that believes that dust actually makes little difference to viewing and that it is better to purchase those binoculars that show honest use rather than a last minute pamper.

Indications of Bad DIY - get a feel for what the exact model or make of binoculars should look like and be aware of additions in the way of screws, nuts and bolts that indicate the binoculars have been taken apart or missing parts have been replaced with inappropriate substitutes. At the same time, you should also consider that some repairs may have been made 'in the field' and with care. These interventions, like those to antique furniture, can be classed as 'honest repairs' and reinforce the premise that these were/are excellent instruments and well worth restoring. 

Indications of Repainting - as already discussed the body of the binoculars unless badly dented/damaged has no impact on the quality of the optics. However, repainting the body can cause many of the working and/or removable parts to become sealed and inoperative. Personally I would avoid heavily repainted pairs of binoculars, removing this sort of paint from joints is a difficult operation. However, if the binoculars are fully functioning and the price is low enough, I would reconsider. 

Collimation - this is when the optics in each side of the binocular are misaligned resulting in two images being seen rather than one. The degree of misalignment can be slight to excessive and if the former is the case then you may be able to use them as is but you will rapidly get eye strain. However, the Recollimation of binoculars is not impossible and you may be able to pick up a bargain even in high end WWI or II binoculars with this fault. I have two Instructables on collimating binoculars and video one for telescopes can be found here https://www.youtube.com/watch?v=hVC9PNHMXM4&t=16s.

IDEAS FOR REFERENCE BOOKS

A great reference book:

Choosing, Using and Repairing Binoculars by J.W. Seyfried. This is my go-to book and although not exhaustive in its detail, contains really valuable information presented in a user-friendly style.

There are some really excellent books for binocular and small telescope astronomy and here are a few of my favourites

Turn Left At Orion by Guy Consolmagno and Dan Davis. This provides the novice astronomer with a great introduction to many striking celestial objects in a simple, clear way. It's a book I still go back to for reference after many years of observing the skies.

Binocular Highlights by Gary Seronik, as a great manual for observing the night sky and again accessible to both the beginner and experienced astronomer.

I also have a great fondness for and appreciation of the books of Patrick Moore and own several authored by him. Binocular Astronomy is in the Patrick Moore Series was written by Stephen Tonkin, who I know from his excellent work 'Amateur Telescope Making', these books too are well worth checking out.

I would further suggest buying these books in the 'spiral' version (where available) as they will get constant use and are more robust in this format.

Happy Hunting!

Andy