57 replies to this topic

[PawPaw]

The chance to compare several vintage 80mm Japanese telescopes from the 1970's got the better of me.  Last year I started doing research on Japanese telescopes from the early 1970'a and their development of Semi-APO and APO designs.  There were three manufactures during this time that pushed the envelope in Japan:  Goto, Nikon and Takahashi.  All three were in strong competition and ahead of the US market.  Dave Trott has several videos on this competition and particularly the advancements Takahashi made in the early 1970's.  Dave's video on the 80mm series can be found here:

 

https://www.youtube....h?v=v1jbt6jU-QY

 

Dave's research prompted me to try and answer a question he posed in this video.  "Hello Nikon, Hello Goto are you awake yet?"  While this thread is going to be about a Moldy Nikon 8cm objective it is also a glimpse into why Takahashi felt so compelled to make such a difficult and bold design with their TS-80's  I think Nikon held one of the keys to this question.

 

So for me taking a chance to compare outweighed the chance that mold caused irreparable damage to an objective.  There also was no photo of the objective so I knew the odds were weighted toward a moldy lens.  Little did I know.  The mold was also inside the OTA and on the metal part of the objective cell.  

 

 

 

 

 

 

 

 

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[PawPaw]

First step was to radiate the objective with UV rays.  This was done for several hours over three days.

 

 

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[dweller25]

Looking forward to this….

[gstrumol]

 

pray, continue ... 

[Kitfox]

Hmmm, a cattle panel observatory...never would have considered that.      A Nikon will shine anywhere, won't it?  I am enjoying your ride!!!

[PawPaw]

Step #2 Test via DPAC before attempting any type of cleaning.  

 

My cell phone camera cannot capture truthfully what I see visually via DPAC.  This mold infected lens displayed, to my eyes,  an excellent DPAC.  I would not hesitate to say it rivals my best Goto and Takahashi objectives.  The focuser presents the exact same intra and extra focal images in DPAC.  I could see the mold spots in focus on DPAC.  Still I was heartened to know what was possible.  

[PawPaw]

Step #3  Gently clean R1 and R4.  

 

At this point I did not attempt to remove the objective from its cell.  More on that later.  R4 was exposed to most of the mold that was growing within the OTA but R1 also had a substantial amount on its surface. I employed the "dab" method of cleaning using a Zeiss lens cleaning towelettes I methodically patted R1 and R4 for over an hour with clean towelettes.  Eventually it removed 90% of the mold on both surfaces.  I was careful not to get too close to the cell edge as I did not want to pull contaminants from the metal cell onto the objective.  After cleaning I again tested DPAC with less mold seen at focus.  Still I could see mold intrusion between the lens on R2 and R3.  The lens looks much better in the first pic.  The second pic shows mold still present on the metal surface.

 

 

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[PawPaw]

Step #4  Do a visual side by side star test with a known good objective.  My pick for the side by side was a TS-80 Semi-APO.

 

Not a perfect night to test but still had steady enough moments to see some nice diffraction rings.  The Nikon 8cm and the TS-80 Semi-apo presented almost identical color signatures intra and extra focal.  In focus both scopes presented almost identical images with no color that I could detect.   The TS-80 had every so slightly brighter image but hard to discern much of a difference.  Both showed the exact same diffraction rings around the test stars. 

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Edited by PawPaw, 19 January 2024 - 06:46 PM.

[PawPaw]

Step #4  Contemplate removal and separation of the lens.  

 

I spent almost 2 months debating if I should attempt to clean R2 and R3.  This Nikon had such a perfect DPAC and the side by side testing confirmed it was a top notch 80mm objective I hesitated to try.  Every time I would look at it over the 2 month period I would see the mold instead of ignoring it as I should have.  As the weather turned cold and I spent less time outdoors it was time to try.  One large obstacle was the retaining ring.  I could not get it to budge as it had four locations around the ring thread that looked like some kind of adhesive glue.  

 

Step #5  Contemplate some more.

 

A pic of the mold between the elements after cleaning R1 and R4.

 

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[clamchip]

Don't you just love the pressure, disassembling an excellent performing expensive high-end objective like this one? 

I have a Goto 60mm lens, a little cloudy between the elements I have been staring at for months too. 

I'm sure your Nikon lens is in good hands.

 

Robert

[deSitter]

Step #4  Contemplate removal and separation of the lens.  

 

I spent almost 2 months debating if I should attempt to clean R2 and R3.  This Nikon had such a perfect DPAC and the side by side testing confirmed it was a top notch 80mm objective I hesitated to try.  Every time I would look at it over the 2 month period I would see the mold instead of ignoring it as I should have.  As the weather turned cold and I spent less time outdoors it was time to try.  One large obstacle was the retaining ring.  I could not get it to budge as it had four locations around the ring thread that looked like some kind of adhesive glue.  

 

Step #5  Contemplate some more.

 

A pic of the mold between the elements after cleaning R1 and R4.

Gotta get it done. Optics should not be "do not disturb". They should be "disturb when necessary but no more."

 

-drl

[Kitfox]

Was/is it as bad as this picture makes it look?  There’s a lot in there, too, if so. Not sure what I would do.  I see too many opportunities for     moments.

 

I need to look at my cell and see how similar it is; I don’t remember any glue on it.  On your earlier post, it looks like sloppy application of glue to lock the collimation screws that got into the ring…is that the same stuff?

 

 

Step #4  Contemplate removal and separation of the lens.  

 

I spent almost 2 months debating if I should attempt to clean R2 and R3.  This Nikon had such a perfect DPAC and the side by side testing confirmed it was a top notch 80mm objective I hesitated to try.  Every time I would look at it over the 2 month period I would see the mold instead of ignoring it as I should have.  As the weather turned cold and I spent less time outdoors it was time to try.  One large obstacle was the retaining ring.  I could not get it to budge as it had four locations around the ring thread that looked like some kind of adhesive glue.  

 

Step #5  Contemplate some more.

 

A pic of the mold between the elements after cleaning R1 and R4.

Edited by Kitfox, 19 January 2024 - 09:27 PM.

[dnrmilspec]

Gotta get it done. Optics should not be "do not disturb". They should be "disturb when necessary but no more."

 

-drl

+1 on this. 

 

There is a chance you will mess something up but if you succeed the payoff is enormous. 

 

Success is not final, failure is not fatal: it is the courage to continue that counts.
Winston Churchill

 

“The brave do not live forever but the cautious do not live at all.”

 

“The bravest are surely those who have the clearest vision of what is before them, glory and danger alike and yet notwithstanding go out to meet it.” Thucydides

 

Do not let us down.  We will all be deeply hurt if the dear lens does not see glory again but don't let that bother you.  And, of course, profoundly impressed and filled with joy  if you resurrect it.

 

No pressure though.

[jgraham]

I always have the same debate when refurbing an old achromat. I spent much of my career working with optics and I still get nervous taking them apart, but in the end I do what I gotta do, one careful step at a time.

[Kasmos]

Unattended mold will eventually ruin the lens so I'd have to dig in carefully with the proper tools and a thought out plan. Also, when it comes to an old and dirty neglected lens, I much prefer taking them out and soaking/bathing them over any kind of careful dabbing and wiping in a cell.

Edited by Kasmos, 20 January 2024 - 01:37 AM.

[clamchip]

I plan it like a brain surgeon. Check everything, mark everything and perform the procedure.

It's a high like no other, I love it, before during and after. 

I know I have no choice, it must be done.

What scares me more and is even more rewarding is cleaning eyepieces. It's celebration time

after successfully cleaning a 4mm.

 

Robert

[davidc135]

The pro arguments for disassembling and thorough cleaning are much stronger than the cons.

 

On the latter side the presence of glue complicates things. If that can be easily softened then the next minor potential issue is causing a chip removing the objective from the cell but with due care that shouldn't happen.

 

After noting the lens orientation and measuring the spacer thickness, if they are removed, the lenses can be soaked/washed in soapy water, rinsed and drained.

 

The only uncertainty is weakening the dobs of glue and removing the retaining ring but I expect solvent would do the trick.

 

David

Edited by davidc135, 20 January 2024 - 05:14 AM.

[starman876]

the lens looks beautiful

[deSitter]

I plan it like a brain surgeon. Check everything, mark everything and perform the procedure.

It's a high like no other, I love it, before during and after. 

I know I have no choice, it must be done.

What scares me more and is even more rewarding is cleaning eyepieces. It's celebration time

after successfully cleaning a 4mm.

 

Robert

I always think of it as an Alfred Hitchcock movie. He storyboarded everything. Every shot was absolutely set in his head before they did the take. As a result, he got movies finished under budget and on time.

 

So I hear that "dah dump, dah dah dah dah dump de dump..." when I start

 

-drl

[PawPaw]

Thanks everyone for their input and knowledge.  I am and was in agreement on the damage mold can do and it should not be ignored.  I tend not to disassemble or clean objectives unless they really need it.  Dust, dew/condensation marks for me don't fall into this category.  Even though the mold is visible via DPAC at null I could not detect any detrimental effect on the side by side test with the TS-80.

 

A few days ago I laid out my plan for disassembly and cleaning.  My goal was not only to remove the mold but document the cell itself as Nikon states the following about it.   The pic was ran through a translator so keep that in consideration. 

 

  

 

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[Ian King]

I am going to be keeping a very close eye on this thread, I also have a Nikon 80mm F15.

 

It is one of the sharpest 3" refractors I have ever used but like my Vixen 102 F15 it rarely gets out under the stars because it is just not grab and go.

 

The tube is built like the proverbial battleship and it is well over twice as heavy as my modern Scopetech 80mm F15; which as long as you are careful is grab and go.

 

So this thread got me thinking, what if I swopped the OG from the Nikon into the Scopetech?  

 

Removing the OG from the Scopetech was a breeze, the Nikon on the other hand needed warming with a hair dryer before I could convince the lens to come out easily.  But to my delight both lenses are identical in diameter and thickness so the Nikon lens popped straight into the Scopetech cell.

 

A quick indoor artificial star test shows perfect collimation.

 

I guess this might sound like sacrilege to some but I can easily pop the Nikon lens back into its original cell at any point and now it will see more use.

 

PS not trying to thread hijack - but this thread was what inspired me to do the swop.

Edited by Ian King, 20 January 2024 - 09:59 AM.

[apfever]

try

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[PawPaw]

Was/is it as bad as this picture makes it look?  There’s a lot in there, too, if so. Not sure what I would do.  I see too many opportunities for   foreheadslap.gif  moments.

 

I need to look at my cell and see how similar it is; I don’t remember any glue on it.  On your earlier post, it looks like sloppy application of glue to lock the collimation screws that got into the ring…is that the same stuff?

 

 

Kitfox it was as bad as the pictures look.  The OTA had heavy mold toward the objective end and lessened toward the focuser.  Some of the heavier areas behind the objective etched the black paint inside.  I removed the first baffle (compression fitting) on the objective end and wiped as far as my arm would  reach with a mixture of bleach water.  I replaced the first baffle and submersed the entire OTA in a bleach water bath and rinsed and let air dry.  The baffles are held in by compression very fine metal plus they also had adhesive on three spots toward the objective side.  This made it easy to reinstall the first baffle as I could see exactly where it was glued.

 

As for the cell collimation screws I can't call it "sloppy" as they applied the adhesive to the side of the screw where it mated with the cell.  I believe they did not want to cover up the screwdriver slot.  The retainer ring had what looked like the same adhesive in 4 spots.  

 

First pic is focuser end of OTA.  Second pic shows how some of the mold etched the paint inside.  The flat black paint held up well and the baffles are well made.

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Edited by PawPaw, 20 January 2024 - 10:31 AM.

[PawPaw]

After the OTA cleaning I did one more  UV session for several hours with manual tracking.  

 

 

 

 

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[DAVIDG]

 The instruction sheet states the lens is  anastigmatic design which a standard Fraunhofer design is.  I would check the uniformity of the air gap before you take it apart by shining monochrome light on it and observing the interference rings between the elements.

   The lens cell  looks like typical push pull type to collimate it with a threaded retainer ring to hold the lens in place. If so you shouldn't  have to remove the push pull section, just the retainer ring to remove the elements.

   The standard  "wine glass" method of placing the lens over a cylinder and dropping the cell away from the lens leaving on top the support. should be used.  I would place a piece of cardboard over the lens when you loosen the retainer ring just in case the wrench slips. It has saved me a couple of times ! With the lens out the cell you can then carefully separate the elements. Usually the spacer will stay on one element. If so the other element can be fully washed. The one that still has the spacers can be carefully cleaned. The cell should be thoroughly cleaned to remove any mold. 

  The spacers should be checked that there are at 120 ° centered and the same distance from the edge. The lens is now resembled and placed back in the cell. Using monochrome light the interference rings are observed and the retainer is screwed down just enough to make the rings perfectly round and centered. This should be with only a bare minimum amount of pressure so the lens still can move.

    The lens cell is then installed in the telescope. A laser collimator is placed in the focuser. The tilt of the focuser is adjusted so the laser passes through the exact center of the lens. The telescope is now pointed at a wall a couple of feet away. You will see one bright laser spot and a couple of fainter one around the bright one. The tip/tilt of the cell is adjust to bring  all the spost on top of the bright one. Your lens is now clean and perfectly aligned.

 

                 - Dave