57 replies to this topic

[dnrmilspec]

I am not sure you are accomplishing a lot by baking organic material into your glass/coatings.  I am no expert but I did some quick research about this last night. 

 

There is an procedure in medicine called ultraviolet germicidal irradiation which, when the correct wavelength is concentrated on an environmental surface, can kill certain organisms including molds.  The thing is that several things are happening in your lens.  You are likely heating it considerably and if enough, you would be baking the organic compounds into the lenses.  Just like food in an oven, it is possible you are making it much harder to remove using gentle techniques. 

 

I know that we have used solar projection through scopes the size of yours for a very long time without damaging them.  The thing is that this relies on the clarity of the lens in large part, to allow light to pass without excess heating.  Your lens is not, at the moment, particularly clear.  Sky and Telescope recommends stopping down any lens to less than 3" for solar projection and you are just over that now.   If you are getting even moderately high temperatures in the lens you are also baking any cement that may have been used in the construction of the lens or other material in the cell and spacer. 

 

So my opinion is that you ought to stop baking the lens and cell in the sun.  It may not feel especially hot on the outside but it may still be too hot for comfort.  And, at the end of the day, the best case scenario is that you are left with dead mold in the objective with the areas of the objective shaded by the metal of the cell probably still containing viable spores. The cardboard spacers mentioned above come to mind.

 

Once you have disassembled and cleaned  the lens and components, a bleach bath and careful rinsing will have killed any remaining mold spores.  You did this with the bleach bath for the tube and then put the "infected" lens cell back in it if I read correctly.

Edited by dnrmilspec, 20 January 2024 - 10:47 AM.

[PawPaw]

Not only did I DPAC test this lens first I also, as David suggests above, confirmed  the uniformity of the interference rings.  They were centered and concentric and very fine.....similar to some of the Goto's I own.   

 

Time for removal.  The inner objective cell only makes contact with the OTA cell via a lip where the collimation screws mate up.  There is quite a large air gap between the rest of the inner and outer cell.  This was surely by design and helps with thermal stabilization.  As for the retaining ring I used a non-acetone based nail remover my wife has.  Using a qtip I applied it sparingly on the four locations that looked like adhesive.  After 30 min and 3-4 applications the retainer ring finally gave up!  With that I setup my normal lens removal station and washed my hands and brushed my fingertips with dawn soap.  two clean cotton towels laid out on the counter with lots of light and of course my best set of reading glasses  .

 

 

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[PawPaw]

The retaining ring held in place a spacer (looks to be some kind of plastic not metal)  that has three raised points designed to be placed directly over the spacers at 180 degrees.  The Takahashi cells I own (TS-80) have the same type (except theirs is metal)  of retainer spacer.

 

 

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[clamchip]

Sometimes the spacers are all cemented to the flint and feel stuck but never trust it.

I place a paper towel or a coffee filter over the drain hole, or just plug the hole.

If a spacer does get accidently removed by the cleaning in won't go down the drain.

Yes it happened to me, only once and oh what a pain.

 

Robert

Edited by clamchip, 20 January 2024 - 11:13 AM.

[DAVIDG]

 Slots in the retainer  spacer are  for temperature compensation.  It keeps  slight but even pressure on the elements so they don't get pinched with temperature change.  You see this on high end optics and like I said in another thread the  old opticians knew how to figure glass and were also excellent engineers in designing the cell to maintain the figures they put on the glass. Make sure that the three raised areas are  positioned back over the spacers. You also should find that there are three raised area on the rear surface of the cell that the lens rest against. Again the spacers need to over these areas.  Pressure is only applied to the areas were the spacers are located and at 120° centers. This allows one to achieve perfectly  uniformly air space and round and centered interference rings.  

  It is critical that you don't over tighten the retainer  or you will defeat the excellent engineering that went into  the cell. 

 

               - Dave 

[PawPaw]

And after much trepidation and 53 years the Nikon 8cm is released from its cell.  Nikon painted the edges of their objectives, added one alignment mark in pencil (at an angle so the lens can only line up one way....smart)   and the edges of both the flint and the crown are finely chamfered.  The spacers are glued to the Flint and are curved and very very thin in width.  

 

I added a second pencil mark on the original one to make a > pointing toward the crown.  Also added small pencil marks identifying where the spacers were on the flint edge before separation.  Note the first picture shows the white mold on the edges.  The mold residue brushes off easily so it seems not to be actively growing anymore but the damage may have already been done. 

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Edited by PawPaw, 20 January 2024 - 11:30 AM.

[PawPaw]

Note how finely curved the spacers are.

 

 

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[PawPaw]

Lukewarm water rinse followed by a drop of dawn dish soap  on each surface.  With clean fingertips I very lightly lather the entire surface letting the soap pull any contaminants and re-rinse.  I do this 2-3 times followed by a distilled water rinse.  The mold residue was removed without any scrubbing which to me points to the fact it was not actively growing.  After the rinse I lay the lens at an angle against a glass wrapped with a cloth and using an air puffer the water drops that remain are blown off to the edge.  Once both sides are removed of all small droplets and the edges are dry I let it air dry for 10-15 min.  Both the Flint and Crown received the same treatment.  

 

Note the cloth laying in the sink.  I don't want a foil spacer to drop down the drain!  

 

 

 

 

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[starman876]

you are  a brave man doing all that with such a rare lens.

[PawPaw]

I know that we have used solar projection through scopes the size of yours for a very long time without damaging them.  The thing is that this relies on the clarity of the lens in large part, to allow light to pass without excess heating.  Your lens is not, at the moment, particularly clear.  Sky and Telescope recommends stopping down any lens to less than 3" for solar projection and you are just over that now.   If you are getting even moderately high temperatures in the lens you are also baking any cement that may have been used in the construction of the lens or other material in the cell and spacer.

 

So my opinion is that you ought to stop baking the lens and cell in the sun.  It may not feel especially hot on the outside but it may still be too hot for comfort.  And, at the end of the day, the best case scenario is that you are left with dead mold in the objective with the areas of the objective shaded by the metal of the cell probably still containing viable spores. The cardboard spacers mentioned above come to mind.

 

All good points to consider. 

 

 I did ponder was how long to radiate with UV.  You can see one picture where I was holding my hand at the focuser end with sunlight on it.  It was not so hot I had to move my hand away immediately but It was very very warm but not burning.  Obviously I was not using an eyepiece.  I did not track the sun constantly and let it track out of focus for several minutes.  I believe the benefit of a few UV rays could  not hurt.  Plus the old scope just needed to breath a little after who knows how many years inside the cabinet.  There is no cardboard used in construction and the only cement/adhesive used was on the metal baffles (small amount keeping them in place to the OTA tube)  and the cell collimation screws.  

[PawPaw]

The crown and flint after cleaning.  The spacers stayed in place.  I was careful not to put any pressure or scrub while cleaning.

 

 

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[PawPaw]

Both cells were scrubbed clean with alcohol.

 

 

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[mattyfatz]

Robert states he approaches lens cell work like a surgeon, and so do I.. but my mentor is Dr Frankenstein.

 

 

 

Between the rust and the mold I had to steam and boil this Edmund lense cell to get the optics free.

 

 

 

[PawPaw]

It should be noted that before removing the internal objective cell from the OTA cell I marked the orientation and did not remove the smaller push screws.  The collimation was tested prior to removal and was spot on.  My thought was if I re-assemble via the same position then the collimation should still be on.  Of course this will be confirmed later.

 

A few puffs of air between R2 and R3 and voila.  So far so good.  Fingers crossed.

 

 

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[Kitfox]

My heart rate is a little high right now.  SLOWLY coming back down.

 

DAVIDG, I hope you don’t mind, but I have copied your posts here and archived them in a catch-all database I started a few years back. Those are quite worthy of saving, thanks. 

Edited by Kitfox, 20 January 2024 - 12:41 PM.

[PawPaw]

With the cell gently slid down onto the objective the retaining ring was placed with the raised tabs directly over the spacers.  I checked for any raised tabs on the flint side of the cell but could not find any.  It is smooth all around its circumference.  Re-assembly completed, interference rings tested,  collimation confirmed and ready for DPAC.  But first:

 

 

 

 

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[deSitter]

With the cell gently slid down onto the objective the retaining ring was placed with the raised tabs directly over the spacers.  I checked for any raised tabs on the flint side of the cell but could not find any.  It is smooth all around its circumference.  Re-assembly completed, interference rings tested,  collimation confirmed and ready for DPAC.  But first:

"Piece of pie."

 

"Cake."

 

"Cake. Piece of cake."

 

-drl

[PawPaw]

The raised tabs positioned and collimation confirmed.

 

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[PawPaw]

Interference rings centered and one final picture of the restored objective.  

 

One note I want to make is on the coatings.  Amazingly,  to me,  The mold caused no damage that I can detect to the coatings of the lens.  It is unknown what coating technology Nikon applied (most likely proprietary) during this time (Their camera technology gives a clue) but suffice to say whatever they used it withstood the test of time.  The last picture shows the aura of the violet hue.  Another observation I made while cleaning this lens is the ease which I was able to puff away the water droplets after the distilled rinse.  I have cleaned many objectives using this same technique and have always found it time consuming to remove the tiny droplets left on the lens after rinsing.  Usually there is more surface tension between the water and the lens, with this Nikon the droplets were easily removed with one or two puffs.  It almost acted like washing your car after waxing.  I can only attribute this to the coating technology used.  

 

Anyway thanks for watching and contributing.  I hope this thread helps someone in the future as a reference or even what not to do.  

 

Cheers

 

Don

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Edited by PawPaw, 20 January 2024 - 01:43 PM.

[dnrmilspec]

That is just marvelous.  You have restored a treasure.  Way to go!!!

[Kitfox]

Very impressive!  Thank you for sharing. 
 

There are a lot of stories in particular about Nikon, Pentax and Zeiss and their coatings development during the 60s and 70s. Not sure what is being used today is any better than those early multicoatings. 

[dweller25]

Well done 

[apfever]

Way to go Don. Sweet. Now you need another heavy deep project. Stop back by. I still have both Ed 4", and I'm 'done' as Terra put it. A quick run down of projects (not counting finished things) with the F&F is pretty blatant about more than enough projects for lifetime retirement here. I'm also contemplating moving further from big city. My border on metro is way too complicated and I want more land than this postage stamp anyway and a custom build to fade into. On top of that, there's more to the project thing than scopes, vintage Travco, 61 Chriscraft, VW bus, etc. and there is etc. 

[jragsdale]

This thread brings a tear to my eye, marvelous work restoring such a rare classic, great technique and methodical planning.

[Dave Trott]

What a wonderful and rewarding story. I was on the edge of my seat!

 

Thank you, Don!