Necessary dissuasive assistance is requested. Disassemble Leitz phaco Npl 25x objective.

[Sabatini]

Cordial greetings.
Even though I was able to disarm other objectives, all of them achromatic and only 4x 10x 40x, and put them back to work cleaner than before and with the least possible damage against them. Never one with so many elements as this one, I think that NPLs have 10 or 12 elements , always gives quite anxiety a new project of this kind especially because we can end up with one less friend.
Although I do not find the performance of the objetive bad at all , I notice it a little lack of contrast and definition.
You can observe
Through the telescope that in the internal elements there are loose particles like paint and a kind of cloudiness, I would like to reach this element and try to clean it, but in the process i failed to loosen the front elements, Even that I tried with pliers covered with leather and bicycle rubber, I also tried to remove the retaining ring and loosen the elements from the rear but it fails to an so far I have been unable to release them. Now if someone knows if they are released from the front or how it would be done?Would I have to leave them with some solvent for a while to see if they loosen? My other concern is if the alignment of this objective is too strict, it needs a lot of caution to put it back exactly the way it was? Since it's only a 25 x achromatic, it probably won't be as demanding to assemble.
I've been able to read and follow instructions from several previous posts and I find the experts' opinion interesting a very helpfull.Especially those provided by Apo.
Well I hope it will be of interest to someone and above all to find the necessary support from someone who will persuade me to !!!Not!!!.. disassembly this objective.
Thank you.

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[Sabatini]

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[Hobbyst46]

You probably did this already, but in the case you did not --

I would start by blowing air, strongly, into the objective from the thread end, so the wind will carry dirt away as much as possible. Then, if still necessary, I would moist a Q-tip, wrapped with lens tissue or Kim-Wipe, with a mild solvent like IPA or heptane or petroleum ether (NOT acetone, NOT xylene, NOT toluene) and wipe the glass inside.

[Sabatini]

Hobbyst46
Thank you very much for the idea, do you think that to dismantle this lens i should start from the front or from the back? I was trying to hit it to see if the rear element would come out but it doesnt fall back. The front is too hard to unscrew ... suddenly if i added a few drops of solvent it could loosen and unscrew?
How would you approach the disassembly process in the beginning, where to start?

[Sabatini]

In the case of the phaco NPL 16x the whole procedure was very easy to disassemble because all the elements were sliding from the back one after another, then I cleaned them with a few drops of soap, distilled water and a little bit of isopropyl and they were super good but it was very simple just remove the retaining ring and all the elements were coming out from the back, but in this case, it didn't achieve that any element came out from behind, it must be another method that must be applied or used.
For the front did not manage to unscrew any of the brass pieces even though I used several methods such as pliers covered with a leather strap.
How would be the recommendation to be able to disassemble it and make a good maintenance that is well clean ... to see if I can sleep peacefully

[Hobbyst46]

In the case of the phaco NPL 16x the whole procedure was very easy to disassemble because all the elements were sliding from the back one after another, then I cleaned them with a few drops of soap, distilled water and a little bit of isopropyl and they were super good but it was very simple just remove the retaining ring and all the elements were coming out from the back, but in this case, it didn't achieve that any element came out from behind, it must be another method that must be applied or used.
For the front did not manage to unscrew any of the brass pieces even though I used several methods such as pliers covered with a leather strap.
How would be the recommendation to be able to disassemble it and make a good maintenance that is well clean ... to see if I can sleep peacefully

Confession: never tried to disassemble an objective... just thought of how to try and avoid it... sorry, can't help !

[Sabatini]

Ok ...thank you very much, I appreciate it.

[Element 56]

I never took a npl apart but I have rebuilt other Leitz objectives and quit a few others. Usually most of the lenses will need to be removed from the back, however, some are a little of both. When I do an objective that I'm not familiar with I progressively disassemble whatever is easiest first. If you get as far as you can from the front start disassembling the back. When you have everything you can take out of the back out, you will have a better understanding of how to take apart the front. It's a process of elimination.

Yes, it is critical to keep the rotation of each piece of glass and each component as it was and to index them with each other. This is very difficult when removing one piece at a time but you'll have to mark them as best you can. You need to mark the barrel too so you have an index point for each piece as you go. Sometimes the lenses are already marked but don't count on it. Take pics of each piece you remove as you go. The more pics the better. I always seem to end up wishing I had another picture of something. Sometimes I will do drawings too.

Before doing this you need to understand that there will likely be some loss of correction quality because it's unlikely you will get every lens back into it's original position. It may not be very noticeable but as long as you feel it will still be an improvement over what you currently have by all means proceed. Also there's always the chance of breaking something or finding some other problem that you just made worse by taking it apart.

Good luck!
Kirby

[Sabatini]

Kirby.
Thank you for your kind assistance. It is quite true that the procedure becomes a bit stressful at times because the method is trial and error.... you start trying the most obvious and do not know what can happen in the next step, it's like a "I hope this is it, or "God nothing ends up broken" ... I think that ultimately I will leave it alone, I do not want to have to go through an unfortunate "oopss what happened here"
Thank you very much for your willingness to find a solution.

[Element 56]

Sabatini,

I think you made a good decision. Maybe if the lens gets worse you could pick one up on eBay then repair this one as a spare. They do come up and they are inexpensive. They are very good objectives!

Kirby

[Sabatini]

Kirby.
Shame on me, I'm very sick...after all I kept insisting and finally I managed to decipher the puzzle, all the elements came sliding out from the front...after using a few drops of solvent. Then I was marking in its exact orientation ,(well almost), cleaning with distilled water and liquid soap... Brasso, to polish the cylinder and assemble...everything went well and now it is much more contrasted and clear. although I am not sure if I change the depth of field a little bit, I notice something strange there. but I am not very sure, paranoid maybe.
Thanks for your attention.

[Sabatini]

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[Element 56]

That's great I'm glad you made it better! One thing to be careful of is using anything overly abrasive inside the barrel. I overdid it once with prelim and it actually made the barrel slightly oversized. Ultimately it was okay but had I gone much further I imagine I would have needed to shim it.

One thing regarding the depth of field, there is sometimes very thin shims between some of the lens assemblies. If you lose one or misplace it in the wrong position it could potentially change the DOF.

Regards
Kirby

[Sabatini]

Kirby.
Good night and thanks You.
I would not have imagined that it would be possible to overpolish the cylinder and as a consequence leave it too worn, but I do the polishing with cotton so it is very soft and then a quick wash with soap.
I am sending you pictures of the results, I think is improved in a great way, and images of the inside...very clean!.
The procedure is stressful but in the end you get a better sleep.
By the way, no thin shims attached.

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[Element 56]

Although a medium such as cotton won't necessarily increase the abrasive action it is however the abrasive that does the work. So it's just a matter of not overdoing it. You would be surprised how much material one can remove via hand polishing with something like Brasso or Prelim etc..

Yes it can be a stressful thing to have one of your prized objectives in pieces on the bench. No matter how many times I've rebuilt lenses there is still times I get nervous about whether or not it will go back together smoothly and if the end result will have been worth the effort. So far so good!

I'm glad you improved your image! That's a best case scenario!

Kirby