Telescope lens ring removal.

[Guest]

I have a Skywatcher ED 100mm refractor. Last night I removed the objective lens cell. I successfully cleaned the outer surfaces of the crown and flint. I would like to separate these lenses to clean a small amount of mold or fungus before it develops and damages the coatings. A securing ring has to be removed. Does any one know where I can buy a tool to engage with two holes on this ring for removal?

Also has anyone done this before?

When refitting the lenses into the cell do the crown and flint have to go back in the same position rotationally?

I ask this as older achromat lenses did have a so called sweet spot

Edited September 17, 2020 by Guest
Added text.

[johninderby]

You want a lens spanner like this.

https://www.amazon.co.uk/Neewer®-Professional-Stainless-Spanner-Opening/dp/B00J5F6ZI2/ref=sr_1_9?dchild=1&keywords=camera+lens+spanner&qid=1600334008&refinements=p_76%3A419158031&rnid=419157031&rps=1&sr=8-9

[JeremyS]

Good luck with this @Grumpy Martian. I can't bare to watch..... 😧

[DaveL59]

you'd want to mark the lens edges so that you can align to the same orientation when reassembling, a sharpie or wax pencil would achieve that, and make accurate note of where spacers etc are located. However getting the elements optically aligned doesn't sound trivial on these from what others have said on other threads so might be best left to a specialist to do this work.

[Peter Drew]

45 minutes ago, JeremyS said:

Good luck with this @Grumpy Martian. I can't bare to watch..... 😧

Best keep your clothes on then!        🙂

[Peter Drew]

2 hours ago, Grumpy Martian said:

I have a Skywatcher ED 100mm refractor. Last night I removed the objective lens cell. I successfully cleaned the outer surfaces of the crown and flint. I would like to separate these lenses to clean a small amount of mold or fungus before it develops and damages the coatings. A securing ring has to be removed. Does any one know where I can buy a tool to engage with two holes on this ring for removal?

Also has anyone done this before?

When refitting the lenses into the cell do the crown and flint have to go back in the same position rotationally?

I ask this as older achromat lenses did have a so called sweet spot

I think I would try exposing the lens to artificial or solar UV to kill off organic activity.  A small amount of fungus is better than a can of worms!   If you can see fungus it probably has already etched the coating, it will however have negligible effect.     🙂  

[Rusted]

Removing optical elements from a cell is a path drenched in tears! 

If you don't know the correct way then you shouldn't even think about taking the next step.

I shan't say what is in case it encourages others to ruin their precious optics.

 

[johninderby]

[SiriusB]

I've taken most of my objectives out the cells, probably wouldn't reccommend unless theres a need, which it sounds like there is in this case.

If you're too cheap to but the tool a couple of small drill bits or allen keys will often work for removing the retaining ring, not that tight usually (round holes in all the synta fracs i've owned) But the tools are fairly cheap & can be used on EP's too, which always seem locked  tighter & more fraught with a potential slip of makeshift tools &..... hey ho, one scratched field lens later....you wished you'd bought the proper tool.

My main caution would be in the removal & particularly the replacement of the lens elements. sometimes they stick part way,sometimes they really stick too!

When replacing  element,s  you may want to invert the lens cell & gently push both elements up together with a soft cloth, other way round sometimes you get a nasty [removed word] of glass on glass when one element suddenly 'unsticks' itself.

.....Just so you can learn from anothers mistakes.😉

[Robindonne]

The second 100ED in a month.  These microorganisms should have never reached earth😣. Do you have a picture of the condition of the glass?  

Edited September 17, 2020 by Robindonne

[Rusted]

It seems more than one lens abuser needs some advice:

You remove lens elements by lowering the opened cell vertically over a stable, padded support on a clean and stable surface.
The objective remains in mid air as the cell is lowered with more care than an actor defusing a "dirty" bomb in the centre of a large city.

So your lens support had better be tall enough to allow the cell to reach the table safely while leaving the fragile glass suspended and exposed.
A drinking glass, of suitable dimensions, covered in a cloth or tissue, is usually recommended.
The protected circular rim avoids tilting on curved elements. Once free of the cell the objective itself may be highly unstable!

But, at least you have a glass handy to drown your sorrows when you've just made your precious objective into an utterly worthless, decorative object. 
The flint is particularly prone to large, scalloped, surface flaking when your hand shakes.
Or you lose patience with gravity as the lens clings desperately to its cell. It probably has far more sense than you do at this point!

Checking for spacers and marks on the edges of the lens elements should be considered the next vital step.
These are often found in almost invisible pencil. So you'll need a good light and/or torch and your best reading glasses.

Better have that 5 gallon drum of matt black paint and a four inch brush handy to "tidy up" your newly added, lens surface decoration.

Then you can start all over again with the cell surrounding your empty drinking glass ready to be raised around the cleaned objective.
I'd get an ad in the Sales and Wants before you even start. Don't forget to mention the huge scallop on the flint!
Though you can always cover the lens with gaffer tape. Like one person of doubtful heritage selling a folded 6" refractor on UK Buy/Sell.

[johninderby]

Just read a thread on CN where someone wanted to take apart the objective of his Astro-Physics 155EDFS Starfire to clean it but was finaly convinced not to do it. 🙀

Edited September 18, 2020 by johninderby

[DaveL59]

2 hours ago, Rusted said:

The flint is particularly prone to large, scalloped, surface flaking when your hand shakes.
Or you lose patience with gravity as the lens clings desperately to its cell. It probably has far more sense than you do at this point!

 

you mean something like this...

In this case tho the lens "cell" was quite different and just the small step between the inner and outer tubes securing the lens in place and that was enough for the lens to tilt as I was turning the dew shield outer section trying to overcome the glue that was securing the inner and outer sections together. A lesson tho for sure in how fragile the flint glass can be. Now this lens still performs very well after blacking over the spalled part. The rainbow area returned to "normal once out of the cell tho I'm aware it is a weakened area that could fail later on of course.

The above lens is a glued 3-inch vintage doublet where the ED in question is 2 air-spaced lenses of course, so double the opportunity for a lens to decide to go its own way as you try to free it from its prison...

 

[John]

I've removed, split and cleaned a few doublets up to 152mm. I would not try a triplet though. These were older scopes bought for not a lot.

It is a delicate process and great care has to be taken getting the lens elements out of the cell. I used the approach below, once the lens retaining ring was removed. That in itself can be tricky as some manufacturers add a couple of spots of cement to the threads to dissuade people from tampering.

The method is to put a good quality optical cloth over a suitable tubular support which is a little smaller than the diameter of the objective. The weight of the cell then allows you to gently push it back evenly from around the objective elements without disturbing them.

The rear of the objective is sitting on the optical cloth.

Sometimes the lens elements stick together which adds to the complexity. Care has to be taken to note the relative position and orientation of the lens elements (hence the markings) and that the foil spacers or spacing ring are / is not damaged, lost or moved. Replacing the foil spacers has risks as well as their thickness and even spacing around the lens circumference determines the air space between the elements which is critical to the performance of the lens.

Once the 4 lens surfaces have been blown, cleaned and then blown again, re-assembly is a carefully performed reverse process. Keeping dust particles out of the lens gap can be challenging during re-assembly.

So it can be done but I hesitate to recommend it really. The ones I've done were cheaply bought used scopes. 

I've always found myself very relieved to get the objective back together and in it's cell again !

[F15Rules]

22 hours ago, Peter Drew said:

Best keep your clothes on then!        🙂

Please do, Jeremy, for all our sakes!! Or do I need to spell it out for you??🤭

Dave

[Neil H]

Hi guys if you put lens out in the sun that will kill fungus off so no need to take it apart

[Guest]

Well I am grateful for all of your input and advice. Armed with fore knowledge about possible pitfalls I made a ring removing tool with aluminium angle and a 1.5 mm allen key. Carefully removing the securing ring. Not a great deal of resistance. Using the cloth supplied with the Baader lens cleaner kit I turned the lens cell upside down and supported the objective. This moved out nicely. There were Mark's to indicate the correct position of the crown and flint rotationally. I did mark a slight dot on the edge of the crown and on the cell. This was incase the lenses separated before I could ascertain the correct position of both. Two cleans of all surfaces with Baader fluid and using the supplied cloth. I now feel happy that my objective is clean and mold/fungus free. I will of course check the diffraction rings tonight. But feel happy and confident.

Would I recommend doing this? No, take it to an expert. I got lucky today. I was prepared for the worse.But have seen the downside results.

Edited September 18, 2020 by Guest
Text added

[JeremyS]

3 hours ago, F15Rules said:

Please do, Jeremy, for all our sakes!! Or do I need to spell it out for you??🤭

Dave

I thought you might uncover that Dave. Stripped it all back to all butt the bare essentials, as usual! Don't worry: I can handle it.

[johninderby]

I can't bear it 😀

 

Edited September 18, 2020 by johninderby

[Rusted]

Bear the weight? A bear is heavy.

But, you never see a bare bear.

[johninderby]

.

 

 

Edited September 18, 2020 by johninderby

[StevieDvd]

'Bear in mind' the deed has now been done. 

Hope it has all gone as you hoped and views well.

[NVDW]

Tackled my 100ED today too