Lubricating focusser of old Japanese Porro with end cap of focusser shaft locked on solid (1 Viewer)

[Stephen Prower]

Lubricating focusser of old Japanese Porro with end cap of focusser shaft locked on solid

As I recall, a long time ago a poster on an old thread, possibly on BirdForum, said that it was his or her practice when relubricating the stiff focusser of an old Porro to add a little light oil to the original lubricant, but otherwise leave the original lubricant undisturbed.

I wouldn’t normally post, but I have never since reading that post read mention of the same practice again.

The spur is that yesterday I was grateful to the poster for describing his practice. I bought a battered old Japanese Porro that looked as though it might be capable of resuscitation. One job of work that was needed was to relubricate a stiff focusser. When disassembling the focusser of an old Japanese Porro, I usually remove an end cap to expose the end of the focusser shaft. I insert a screwdriver down the shaft, unscrew the focusser locknut, and proceed to complete disassembly.

But last night I couldn’t get the end cap of the shaft of the focusser to unscrew.

I then had a wheeze. I remembered what the poster on the old thread had said. I need not be concerned that mixing two lubricants together might be the wrong thing to do: The focusser of the binocular presently turned so stiffly that the binocular, as it was, was useless to me (or any friend or family member who I might hand it on to). I was in the "Win, Win" situation that I should either get a working binocular now -- or should I eventually get the end cap off, I should get a working binocular in the future.

I got out an oil pen filled with light machine oil. I found a likely place to add oil where the oil might seep through into the threads of the focussing screw, and a place where it might likewise seep through into the threads of the focussing wheel. I added a few one millimetre diameter drops of oil in each place*. It was then only left to wind the focussing screw many times back and fore, and see if this would successfuly work the oil in. It did!

If I’d continued much longer trying and failing to get the end cap to unscrew, and so getting more and more frustated, I’d almost certainly have ended up butchering the screw slot of the endcap. To boot, should the blade of the screwdriver have slipped, I could have ended up stabbing myself with the screwdriver through my hand.


Stephen


* I should have built up a couple of drops at a time (since too many drops might, irreversibly, have made the focusser move too freely instead of too stiffly), and then thoroughly tested the effect each time. But it was late at night, so I left the final big test until the focusser perceptibly began to turn more freely in the intermediate little tests

 

[Paultricounty]

Lubricating focusser of old Japanese Porro with end cap of focusser shaft locked on solid

As I recall, a long time ago a poster on an old thread, possibly on BirdForum, said that it was his or her practice when relubricating the stiff focusser of an old Porro to add a little light oil to the original lubricant, but otherwise leave the original lubricant undisturbed.

I wouldn’t normally post, but I have never since reading that post read mention of the same practice again.

The spur is that yesterday I was grateful to the poster for describing his practice. I bought a battered old Japanese Porro that looked as though it might be capable of resuscitation. One job of work that was needed was to relubricate a stiff focusser. When disassembling the focusser of an old Japanese Porro, I usually remove an end cap to expose the end of the focusser shaft. I insert a screwdriver down the shaft, unscrew the focusser locknut, and proceed to complete disassembly.

But last night I couldn’t get the end cap of the shaft of the focusser to unscrew.

I then had a wheeze. I remembered what the poster on the old thread had said. I need not be concerned that mixing two lubricants together might be the wrong thing to do: The focusser of the binocular presently turned so stiffly that the binocular, as it was, was useless to me (or any friend or family member who I might hand it on to). I was in the "Win, Win" situation that I should either get a working binocular now -- or should I eventually get the end cap off, I should get a working binocular in the future.

I got out an oil pen filled with light machine oil. I found a likely place to add oil where the oil might seep through into the threads of the focussing screw, and a place where it might likewise seep through into the threads of the focussing wheel. I added a few one millimetre diameter drops of oil in each place*. It was then only left to wind the focussing screw many times back and fore, and see if this would successfuly work the oil in. It did!

If I’d continued much longer trying and failing to get the end cap to unscrew, and so getting more and more frustated, I’d almost certainly have ended up butchering the screw slot of the endcap. To boot, should the blade of the screwdriver have slipped, I could have ended up stabbing myself with the screwdriver through my hand.


Stephen


* I should have built up a couple of drops at a time (since too many drops might, irreversibly, have made the focusser move too freely instead of too stiffly), and then thoroughly tested the effect each time. But it was late at night, so I left the final big test until the focusser perceptibly began to turn more freely in the intermediate little tests

I think the oil might be a temporary fix. From what I understand certain viscosities of grease used on for each the hinge, focuser and diopter. Over time the grease hardens and makes it difficult to use the binoculars. I’m having a half dozen of these vintage binos serviced right now and most of them needed to have all the grease stripped and cleaned completely and degreased with the appropriate viscosity grease.

It also depends on the value and collectibility of the binoculars and wether that service is worth it.

Paul

 

[Stephen Prower]

Paul

I agree that the cost of the care that one takes of binoculars should as a matter of good housekeeping be proportionate to the value of the binocular. But I find it hard that I should scrap a binocular as good as say a Swift 748 Triton 7x35, should it need repair, because I can buy a replacement on Ebay for under £50, and a repair will cost more.

I was really addressing people like me who, so motivated, have found out by practice how to re-lubricate a variety of different models of old Porro binocular -- Provided that they can get past the obstacle of a shaft entrance cover that is eg cross-threaded (As I once did to one of my binoculars - I hide my face in shame!) or over tightened!

But in my post I am talking, as you say, about a temporary fix -- Although for all I know the fix could be good for longer than that.

My area of ignorance is (i) the compatibility of lubricants should they be mixed together with each other, and (ii) whether an incompatibility of lubricants can still be harmful in the relatively "slow motion" world of birdwatching., as compared say with the world of vehicles powered by the internal combustion engine.


Stephen


For fun, I have just compared Saturday's purchase, a battered single-coated Kmart Focal 7x35 J-B147 with hard eyecups, with a Swift 748 Triton 7x35, and there is not that much in it! The Swift shades the Kmart perceptibly in my eyes to a degree as to brightness and contrast. It has a closer near focus distance. But the Kmart doesn't lose out much in the ease of view stakes. And important for an old man like me, the more lightly built Kmart weighs 590g against the Swift's 666g

 

[Paultricounty]

Paul

I agree that the cost of the care that one takes of binoculars should as a matter of good housekeeping be proportionate to the value of the binocular. But I find it hard that I should scrap a binocular as good as say a Swift 748 Triton 7x35, should it need repair, because I can buy a replacement on Ebay for under £50, and a repair will cost more.

lots of times even though we can find these nice old vintage wide fields cheap on the bay I’ve found that almost all of them need some service like collimation, hinge And focusers almost not usable and many that a film on the prisms that give the appearance of a cloudy or dark image.

I was really addressing people like me who, so motivated, have found out by practice how to re-lubricate a variety of different models of old Porro binocular -- Provided that they can get past the obstacle of a shaft entrance cover that is eg cross-threaded (As I once did to one of my binoculars - I hide my face in shame!) or over tightened!

I wish I had that ability to disassemble and give them a tune up. I’m all thumbs. I think the Tritons are nice glass for Bk7 and if I could I’d spend the time on them to get them right. I bought a beautiful Swift Sportking that is very impressive and weighs as much as brick.

But in my post I am talking, as you say, about a temporary fix -- Although for all I know the fix could be good for longer than that.

My area of ignorance is (i) the compatibility of lubricants should they be mixed together with each other, and (ii) whether an incompatibility of lubricants can still be harmful in the relatively "slow motion" world of birdwatching., as compared say with the world of vehicles powered by the internal combustion engine.

Im not to up on the different lubricant greases available for these binocular. Cory Suddarth one time had given me a quick lesson on the different products , but it went in one ear and out the other.

Good luck

Stephen


For fun, I have just compared Saturday's purchase, a battered single-coated Kmart Focal 7x35 J-B147 with hard eyecups, with a Swift 748 Triton 7x35, and there is not that much in it! The Swift shades the Kmart perceptibly in my eyes to a degree as to brightness and contrast. It has a closer near focus distance. But the Kmart doesn't lose out much in the ease of view stakes. And important for an old man like me, the more lightly built Kmart weighs 590g against the Swift's 666g

 

[wllmspd]

Personally, if it works then great. But I have tribologists as colleagues and they would likely give a long lecture if I mentioned this. I often taunt them by suggesting WD40 as a lubricant (which it isnt…..).
If you’ve got a really nice pair of Bono’s that need some work give them to a pro for a tune.

Peter

 

[Roadbike]

Paul

I agree that the cost of the care that one takes of binoculars should as a matter of good housekeeping be proportionate to the value of the binocular. But I find it hard that I should scrap a binocular as good as say a Swift 748 Triton 7x35, should it need repair, because I can buy a replacement on Ebay for under £50, and a repair will cost more.

I was really addressing people like me who, so motivated, have found out by practice how to re-lubricate a variety of different models of old Porro binocular -- Provided that they can get past the obstacle of a shaft entrance cover that is eg cross-threaded (As I once did to one of my binoculars - I hide my face in shame!) or over tightened!

But in my post I am talking, as you say, about a temporary fix -- Although for all I know the fix could be good for longer than that.

My area of ignorance is (i) the compatibility of lubricants should they be mixed together with each other, and (ii) whether an incompatibility of lubricants can still be harmful in the relatively "slow motion" world of birdwatching., as compared say with the world of vehicles powered by the internal combustion engine.


Stephen


For fun, I have just compared Saturday's purchase, a battered single-coated Kmart Focal 7x35 J-B147 with hard eyecups, with a Swift 748 Triton 7x35, and there is not that much in it! The Swift shades the Kmart perceptibly in my eyes to a degree as to brightness and contrast. It has a closer near focus distance. But the Kmart doesn't lose out much in the ease of view stakes. And important for an old man like me, the more lightly built Kmart weighs 590g against the Swift's 666g

The machine oil should keep it loose for longer than a bit of lighter fluid or WD40. As the oil mixes with more old grease it may gradually tighten again. Good to see vintage bins back in service after a single fix.

 

[Binocollector]

I often used resin-free sewing machine oil. Worked pretty well so far. I guess it might eventually have to be re-applied.

 

[Stephen Prower]

Lots of times even though we can find these nice old vintage wide fields cheap on the bay I’ve found that almost all of them need some service like collimation, hinge And focusers almost not usable and many that a film on the prisms that give the appearance of a cloudy or dark image.

I wish I had that ability to disassemble and give them a tune up. I’m all thumbs. I think the Tritons are nice glass for Bk7 and if I could I’d spend the time on them to get them right. I bought a beautiful Swift Sportking that is very impressive and weighs as much as brick

Im not to up on the different lubricant greases available for these binocular. Cory Suddarth one time had given me a quick lesson on the different products , but it went in one ear and out the other.

Paul

1. In reverse order, I have a vague and memory that some reliable poster on the Forums said that he used the same lubricant, one of the Nyogels, probably Nyogel 767A, for everything, including presumably focusser wheel and screw. Anyway, as regards wheel and screw, that's what I do. I experiment with different thicknesses of Nyogel for each of them, building up the thickness smear by smear. The solvent I use, when eg I might decide to start all over again, is Petroleum Distillate

2. For the rest of your post, here’s my take! It's just me. Search the Forums, and with luck you'll find someone else who, unlike me, seriously knows his or her stuff.

But first I must apologise. I have edited and extensively re-written this post as now the first part of a two-part post. I went to town in my first attempt at answering you, and ran myself out of time,

This part of the post treats the "How do I avoid buying a lemon?" question, or more accurately, "How do I improve my chances of buying a fault-free binocular?",


Conducting minor repairs to Ebay binocular purchases yourself

1. How do I improve my chances of buying a fault-free binocular?

Anyway: You’ve learned! The name of the game is first to avoid buying and having to return an expensive lemon in the first place. Returns can be a messy business.

By "Lemon " I mean a faulty binocular that is not repairable by you, and also not repairable by a professional repairer (eg Gary Hawkins here in England) at an acceptably low price for you.

Essentially the answer is at the same time to multiply and target your purchases.

To multiply your chances, buy cheap, and buy in a cheap area of the market. You can then buy more than one binocular for your money, and so bear the occasional loss.

But also consider first, before you even start, whether you are capable of exercising the necessary self-discipline for the game. Set yourself rules. The game is notoriously addictive, and liable to create obsessives. Consider whether you have the houseroom for what may eventually become twenty or more binoculars.

I suspect that, as a Forum reader you have already done all this!

Cure yourself of the practice of hunting at random on Ebay for bargains. I speak from experience. It's exciting. But you will definitely run out of house space. There are just too many bargains out there. And bargains are a diversion. Instead target your purchases by buying by specification, no more than one binocular of each specification at a time, until you know what specification or specifications most closely satisfy your particular circumstances.

One very important advice is that you should be biased in your Ebay searches in favour of specifications and models of binocular that survive the years well. I've done well with a couple of Swift Ospreys. They are now duplicated as house and short walk, dry weather binoculars by a couple of lighter weight Swift 748 Tritons. The optical performance of one of the Tritons in turn is also, as testament to its sturdiness, unaffected by a big crack in one of the prisms.

The special category of binoculars that I have done well with in this regard is 1960s and 1970s Japanese "Inspection sticker", and Soviet "Brezhnev years of stagnation" binoculars.

You may not be able to repair these binoculars yourself yet, but you'll cut your professional repair bill. Remember if I, with my limited abilities, can repair possibly 50% of my targeted purchases within two or three hours, Gary Hawkins could put the job out to an apprentice, and the apprentice probably wouldn't need more than half an hour. Or you may have binoculars ready by you that will only need simple repairs if and when you might bite on the bullet, and decide that you must learn from YouTube or wherever how to repair them yourself. And quite apart from all that, you will have incidentally significantly increased your chances of acquiring amongst your new targeted purchases some fault-free binoculars.

Be aware that, to your advantage, there are gaps in the market where prices are lower. The market is swayed by fashion. Presently I believe that among fanciers of old Porros "Extra wide angles", at circa 11* tfov, are in, and "Featherweights", at circa 7.0* tfov, are out. Learn the less favoured specifications and models. The bulky Soviet Tento 7x35 wide angle at 8.5* tfov falls between the above two categories. It has a much steadier market, I suspect amongst persons with big hands who are more into looking through binoculars, than at them.

During the past year I have made just three targeted Ebay purchases. I managed to buy the two Swift 748 Triton 7x35 Featherweights, and as a lighter weight and less ostentatious "Carry everywhere" binocular, a battered Japanese-licensed Zeiss 8x30 Jenoptem. I paid £65 in total for the the three of them. All of them were technically usable out of the box. To make them fully serviceable, I just needed to clean off the dirt from the ocular lenses of the Jenoptem, and to relubricate the focussers of the two Tritons. I've only glanced at Ebay once or twice since, and have hopes that the three purchases have at last cured my own embarrasing Ebay obsession.

Your block is disassembling focussers and reassembling them correctly. I suspect that you could do it if a person repaired a focusser in front of you. First the demonstration would reassure you that you would encounter no confidence-undermining hiccups when working on that particular focusser. Second the demonstration would show you how to do the job. And third the person could guide you as you repeated the job for sufficient repetitions to reassure you that you could now do it on your own.

Then, had you been in my position, you too would have scored a lucky three serviceable binoculars out of three Ebay purchases.

(The Kmart Focal 7x35 was a non-serious charity shop purchase. The volunteer at the cash desk reduced the price from £10 to £5 while I was looking the Kmart over. It had been hanging about the shop for over a month. So I bought it as a challenge, and promised to add a donation of £5, which I shall now up to £10, if I could get it to work properly.)

I shall conclude this part by listing an additional three general cautionary targeting "Rules" that I've evolved for myself in the course of my Ebay obsession:
(i) Avoid Compacts: They are often beyond the capacity of amateurs--and may be difficult also for professionals--to repair. I may have been unlucky in my purchases of faulty Compacts. It could be because of abuse by their owners. But Compacts might also be fragile
(ii) Avoid new Roofs: There are too many people out there chasing too few binoculars. There are too few binoculars on the market, first, because Roofs are usually newer than Porros. Second, Roofs are now, as I understand, either inherently as a design less likely to than Porros to develop faults, or certainly to be damaged, than Porros. Or by he passing of the years Roofs have by progressive refinements become less likely to develop faults or be easily damaged. So by the operation of the law of supply & demand, Roofs are an expensive market
(iii) Avoid old Roofs: I am not sure how robust old Roofs are; but the performance of Roofs in the past, as I understand, took a long time to catch up with the performance of contemporary Porros.

You can work out for yourself where that leaves you!

As I believe you have!


Stephen

 

[Paultricounty]

Paul

1. In reverse order, I have a vague and memory that some reliable poster on the Forums said that he used the same lubricant, one of the Nyogels, probably Nyogel 767A, for everything, including presumably focusser wheel and screw. Anyway, as regards wheel and screw, that's what I do. I experiment with different thicknesses of Nyogel for each of them, building up the thickness smear by smear. The solvent I use, when eg I might decide to start all over again, is Petroleum Distillate

Very interesting.

2. Here’s my take! It's just me. Search the Forums, and with luck you'll find someone else who seriously knows his or her stuff.

I have a few experts on speed dial.

Anyway: You’ve learned! The name of the game is to avoid buying an expensive lemon in the first place.

Yet still buy a dog now and then. Learning what’s good and what I would want is more than meets the eye.

So buy cheap, buy in a cheap area of the market. You can then buy more than one binocular for your money, and so bear the occasional loss.

Theres a whole lot of cheap garbage with old vintage bins. Learning which ones are the high quality variants has been a lot of fun.

But also consider first, before you even start, whether you are capable of exercising the necessary self-discipline for the game. Set yourself rules. The game is notoriously addictive, and liable to create obsessives. Consider whether you have the houseroom for what may eventually become twenty or more binoculars.

To late to exercise self discipline, that ship has sailed 🤪. At this point addictive an obsessive are my nick names. 20 binoculars is crazy, I’m well past crazy.

Cure yourself of hunting for bargains. I speak from experience. You definitely will run out of house space. There are too many bargains out there. Start by buying by specification, no more than one binocular in each specification at a time, until you know what specification or specifications most closely satisfies your particular circumstances.

Ive collected most of the vintage high quality wide field bins I was after , still looking for two more to finish what I started. After that I’ll stop, I’ve promised., really 😉🤫. I'm very lucky one of my children had moved out and I now have an additional office (because that’s what I call it) but really it’s the optics, and hobby room. Plenty of well Air conditioned humidity controlled room in there, for many more dozens
of binos and other man toys.

It is very important advice that you should be biased in favour of specifications and models of binocular that survive the years well. I've done well with a couple of Swift Ospreys. They are now duplicated as house and short walk, dry weather binoculars by a couple of lighter weight Swift 748 Tritons. The optical performance of one of the Tritons in turn is also, as testament to its sturdiness, unaffected by a big crack in one of the prisms.

Be aware that, to your advantage, there are gaps in the market. The market is swayed by fashion. Presently I believe that among fanciers of old Porros "Extra wide angles", at circa 11* tfov, are in, and "Featherweights", at circa 7.0* tfov, are out. Learn the less favoured specifications and models. The bulky Soviet Tento 7x35 wide angle at 8.5* tfov falls between the above two categories. It has a much steadier market, I suspect amongst persons with big hands who are more into looking through binoculars, than at them.

Yes the wide field and ultra wide field bins seem to be the getting more popular.

You’ve probably already learned the general rules:
(i) Avoid Compacts: They are often beyond the capacity of amateurs--and may be difficult also for professionals--to repair. I may have been unlucky in my purchases of faulty Compacts. It could be because of abuse by their owners. But Compacts could also be fragile

totally agree.

(ii) Avoid new Roofs: There are too many people out there chasing too few binoculars. There are too few binoculars on the market, first, because Roofs are usually newer than Porros. Second, Roofs are now, as I understand, either inherently as a design less likely to develop faults, or certainly to be damaged, than Porros, or by passage of the years have become by progressive refinements less likely to develop faults or be easily damaged. So by the operation of the law of supply & damaged or demand, they are an expensive market
(iii) Avoid old Roofs: I am not sure how robust old Roofs are; but the performance of Roofs, as I understand, took a long time to catch up with the performance of contemporary Porros.

Be patient--Be Mr Micawber! Don’t be too greedy for a particular model of binocular to wait for one at the right price to come along. But don't be excessively mean. Favour knowledgeable sellers in cheap markets who supply useful descriptions. Favour institutional sellers who offer no fault returns. Favour local sellers so that you can try before you buy. Avoid ignorant private sellers on Ebay -- You may be able to tell a widow without a qualm that her deceased husband’s old Nikon 8x30E that you snapped up for £30 (or worse snapped up for more) is trashed and worthless, and explain to her that she must agree a return – I am not.

been there done that 😞.

Learn the essential questions to ask a seller regarding the condition of the binocular. Several posters on the Forums have listed their own set of questions. They are, as I remember, all much the same. Even if the seller doesn’t have the understanding to answer the questions, you will often be able to gauge whether or not he or she is the sort of anonymous seller--ie stranger--who you would be happy to conclude a transaction remotely at a distance with.

I have a boiler plate paragraph of multiple questions I copy and paste when contacting a seller before making an offer. Sometimes you could tell more by what they don’t answer then what they do.

Thx Stephen , all good stuff.

Paul

Hoping this helps


Stephen

 

[Binocollector]

An, the addiction of old binos. I stopped after I filled one cupboard and a few crates that are stored under the sofa.
But every now and then... I'll still get more 😂.
Considering that I almost never (except for my Komz 7x30 BPO "Sekonda") paid more than 30-60 € on average (my cheapest find was actually a Kamakura 7x35 for 15€ and a Russian Sotem 10x50 for 17€) - it's a fun hobby. Definitely more fun than other stuff I collected.

 

[Paultricounty]

An, the addiction of old binos. I stopped after I filled one cupboard and a few crates that are stored under the sofa.
But every now and then... I'll still get more 😂.
Considering that I almost never (except for my Komz 7x30 BPO "Sekonda") paid more than 30-60 € on average (my cheapest find was actually a Kamakura 7x35 for 15€ and a Russian Sotem 10x50 for 17€) - it's a fun hobby. Definitely more fun than other stuff I collected.

Hey Philipp, Got any FPO or Kowa rangemasters you want to sell me buddy, pal 🙏🏼👊🏻

Paul

 

[Stephen Prower]

... To late to exercise self discipline, that ship has sailed 🤪. At this point addictive an obsessive are my nick names. 20 binoculars is crazy, I’m well past crazy ...

... Ive collected most of the vintage high quality wide field bins I was after , still looking for two more to finish what I started. After that I’ll stop, I’ve promised., really 😉🤫 ...

Paul

The shades are off! A 20+ man!

"Ive collected most of the vintage high quality wide field bins I was after , still looking for two more to finish what I started."

"Love's old sweet song!" There's two answers to an addict: (1) Dr Tinkle to Matron: "Matron, Matron! I'm a weak man" Matron to Dr Tinkle: "Once a week is enough for any man"; and (2) the rule of life "Leave a party while you're enjoying yourself!". I once walked past Kenneth Williams in the Strand. He was a short man, and was looking daggers at people walking past him, daring them to recognise him. I didn't dare!


Stephen

 

[Binocollector]

Hey Philipp, Got any FPO or Kowa rangemasters you want to sell me buddy, pal 🙏🏼👊🏻

Paul

Unfortunately, no. And if I did, I wouldn't sell them .
I never saw any vintage Kowas on German eBay so far. Tons of USSR binos and Zeiss though. And the lower-end Japanese porros.

 

[Stephen Prower]

An, the addiction of old binos ... it's a fun hobby. Definitely more fun than other stuff I collected.

I might have collected MZ 250 motorcycles if I'd stayed in one place, and had had room to store them -- the first and last of the three MZ 250s I owned were "fun" bikes. If you knew them I had the first model to be imported into Britain: a new MZ Trophy ES250/2 with fitted legshields -- Banana tank, front swinging arm, etc. It was the favourite of all my bikes

Stephen

 

[Stephen Prower]

Have now managed to free the end cap!

In the original post of this thread I reported that I had been unable to free the end cap of the focusser shaft of an old Japanese Porro. I can now report that, after some 10 days trying, I have now succeeded in freeing the end cap*.

I ran a little penetrating oil each night around the base of the head of the cap where it was seated upon the body of the binocular. The cap has a slot for a 15mm screwdriver in it. I tried each night using a screwdriver to turn the cap. Eventually, even though I was applying less than full force with the screwdriver, the cap just came off.

I am not a mechanic. This was the first time that the advice to soak a stuck screw, or stuck anything, patiently in a releasing fluid for several days--or longer--had ever worked for me!


Stephen


* There was still a point to freeing the end cap: The near focus distance of the Kmart Focal 7x35 was too long for me, so I wanted to tweak it (by resetting the point when the wheel bites on the screw) a little. And the serrated outer rim of the focussing wheel had proved uncomfortable for me, especially when birdwatching in cold weather without gloves on my hands. So freeing the cap enabled me to stretch a rubber band (I cut them, as posted elsewhere, from discarded bicycle inner tube) over the rim

 

[Stephen Prower]

Releasing fluid

I should add a warning to my last post. I think that it is the unanimous advice on the web not to use releasants like WD40 on optical instruments: It gasses; it migrates; and it is almost impossible to clean off optics

Stephen