Telementor 2: service and restoration

[markse68]

I bought a Telementor 2 sight unseen and when it arrived discovered it had several issues- some mechanical and some optical. In this thread I’ll be trying to restore it to good useable condition.

Firstly the objective. This was in a sorry state when the scope arrived. A layer of baked on dust covered the front surface. I carefully swabbed this off with isopropanol and lint free cloths disposing of them regularly to avoid scratches. This revealed the rear surface was also in a bit of a state so I removed the lens cell and attempted to swab that clean in the same way. It came mostly clean but there was left a circular patch that just wouldn’t shift with this gentle cleaning.

The patch would catch light from the side and as reported in another thread seemed to be diffusing the incoming light causing a lot of glare/flare whatever it’s called around bright subjects. My thought was it was some sort of fungal etching of the glass surface which doomed the scope to the scrap heap. It certainly looked like that through a loupe.

 

I’d arranged with the seller to return it for a refund but the views through it of the moon were still pretty great despite the flare and I’ve grown attached to this thing the few days I’ve had it... So today I threw caution to the wind and did something pretty foolhardy.

Unscrewing the 2 screws on the focuser to remove it 

 

 

The inner OTA proper can now be removed- tip the assembly until it slides forward then turn the inner tube 90deg to clear the inner guide pads and extract. Note the 3 baffles inserted into slots in the tube.

The lens cell simply unscrews from the OTA.

 

Using just thumb nails in the slots in the retaining ring, unscrew it and remove it and the spring loaded clamping ring. Invert the cell to remove the objective.

 

I used lots of running water, fairy  liquid, isopropanol and a final rinse of distilled water with very gentle finger dabbing to clean both surfaces

After drying a few streaks still remained- the distilled water obviously wasn't perfect

An hour or so using lens tissues to carefully wipe off breath condensate and finally things looked much better

 

DB673276-B135-4DDF-AAD1-AAE551C9F27F.MOV

 

Back in the cell- there was a pencil line on the edge of the glass to mark orientation- and holding it up to the light the circle of diffusion has gone. It’s not 100% perfect- can still see very faint marks on both surfaces with a loupe but it’s much much better. Will try it tonight if there’s the opportunity and see how much improved it really is.

 

This was a pretty stupid thing to do but I’m glad I did it. I could have dropped it and ended up with an expensive pile of junk.

I don’t think I put a scratch on it though so it worked out for the good. I’m keeping the scope 😉

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited May 2, 2020 by markse68
image positions

[RT65CB-SWL]

Looking good! 

[John]

Well done !

I didn't realise that the Telementor used a cemented doublet. Easier than messing around with 2 elements, spacers etc !

 

[markse68]

2 minutes ago, John said:

Well done !

I didn't realise that the Telementor used a cemented doublet. Easier than messing around with 2 elements, spacers etc !

 

The 2's did John- I think earlier ones were air spaced and some say better for it. But yea then there would be a lot more surfaces to clean!

[DaveL59]

Nicely done there, sometimes it's worth cracking something open and having a try, kinda how I've learned much of what I have done so far tho that was on much lower cost items like old binos. Know what you mean about taking the risk though, a plastic bowl in the sink might've been a good idea but I see you thought of impacts with the microfibre cloth just in case  Fingers crossed you get good viewing and maybe it's a keeper after all!

[Dave1]

That's looking good! Much better. Keep this up and you will have a great telescope.

[Alan White]

I can see why you did this, it’s what I would have done.

Hope it works out well, looks like it will.

[markse68]

While I had the inner OTA removed, I took the opportunity to smarten up the “dew shield” part of the outer tube- slight corrosion had left it looking a bit sad. Light wire wooling  to  get rid of the loose stuff

masked of the outside and stuffed a ball of tissue inside to stop the paint going too far

nice and black again- I used high temp exhaust paint which is quite matt though I really should invest in some of that super black stuff for jobs like this

 

Edited May 2, 2020 by markse68

[DaveL59]

might be worth giving the tube and various bits a wipe over with peroxide to cull any spores so the dreaded fungus doesn't creep back to spoil the party when you get to doing deeper resto works

[markse68]

7 minutes ago, DaveL59 said:

might be worth giving the tube and various bits a wipe over with peroxide to cull any spores so the dreaded fungus doesn't creep back to spoil the party when you get to doing deeper resto works

I’ll think about that thanks Dave- doesn’t peroxide react with aluminium though?

[markse68]

Oh I forgot, been looking at the moon and Venus this evening and it still works! 

It does seem better- there’s still purple haze around Venus but less I think and the image is nice and sharp. Probably atmospherics as it was getting quite low but I almost thought I could make out some detail on it! Moon is lovely and rich and contrasty- much less noticeable purple fringing on the limb and nice crisp detail. Couldn’t make out any of Plato’s craterlets but the 6mm is my highest power at 140x. Even the big beast could only see 3 or maybe 4 at more than double that power. 

These fracs aren’t very comfortable to look through though are they?! 😉 need to sort out a 1.25” fitting so I can use my diagonal

[DaveL59]

hmmm hadn't thought of that, but I'd be wiping over with distilled water after too just to be sure then letting it dry out properly before reassembly. I've usually done that with the binos I've collected and worked on, being vintage and not wanting them to grow fuzzies when I'm not watching. Not needed to on the TAL scopes so can't give a definitive answer. Some form of treatment could be worth doing if they had fungus just to be on the safe side, bleach, diluted?

Does look a nice scope now you've recovered the lens, paint's not bad on it either, just the EP's and mount needs sorting. I'm part way through restoring one on the TAL reflectors, full repaint, hopefully it'll look good once done, spent more on paint than for the scope!

 

[markse68]

Lastly today,  I serviced the focusing which was quite stiff as seems to be common.

the focuser is a kind of friction drive Crayfordish design with a tapered hardened steel wheel pressed into a steel U channel mounted in the top of the inner tube.

 

The inner tube is supported by 2 sets of ptfe pads inside the outer tube. At the front there are 2 fixed lower pads and a spring loaded third pad.

 

 

At the focuser end there’s just the 2 fixed lower pads and the wheel makes the third point of contact.

 

The focus wheel is pressed into contact by 2 spring plates acting directly on the focuser shaft either side of the wheel. 2 grub screws allow for adjusting the contact pressure.

 

 

firstly I cleaned everything

 

 

I cleaned the PTFE pads with a lighter fluid soaked pad of tissue paper taped to a long screwdriver- can't fit my hand inside the tube. You can remove the PTFE pads undoing the screws from the outside of the tube but it'd be tricky to replace them

I did contemplate waxing the outside of the inner tube but it's actually quite smooth and low friction with the PTFE so I just gave it a clean with lighter fluid.

 

Then I made things worse. Much worse!

 

I figured for better friction the wheel/U channel should run dry. Big mistake! The result was a nasty graunchy stiff focus that you could feel wouldn’t last very long! This might be of interest to you @Stu if you didn’t know it already- the U channel must be lubricated.

I used some nice sticky blue Mobil grease I had. It stays where you put it and doesn’t separate to oil and soap like regular lithium grease. It pongs a bit though 😉

grease everywhere and now the focus is nice and smooth- not moonlite or feathertouch smooth, but very useable.

 

 

Edited May 4, 2020 by markse68

[Rob]

Very well done Sir. Not a stupid thing to do at all!. You have fully serviced your vintage scope - brought the life back to it. 

Looks really great now. I've done the same many years ago with a Vixen 102m (air spaced doublet). Sure a little scary, but to be fair if you mark the optics where possible and take pictures as you go.. your good.

Enjoyed the post enormously thanks for sharing!. Now enjoy the scope

Rob

[estwing]

Serviced mine few years back as I've had it since leaving school..35 years😱....just could not get get the lens out, cement is so strong I feared I was going to damage something. Great scope that punches above its weight. Well done on keeping it going.

 

[Doc]

I'm so pleased you took the plunge and done this. It's not that hard if you take it step by step and fully prepare yourself with the right kit. Well done that man 👍

[markse68]

4 hours ago, estwing said:

Serviced mine few years back as I've had it since leaving school..35 years😱....just could not get get the lens out, cement is so strong I feared I was going to damage something. Great scope that punches above its weight. Well done on keeping it going.

 

 

Which cement @estwing? On the retaining ring? Mine had a tiny little dab of varnish to lock it but it span out really easily.

[RT65CB-SWL]

I have been following this with great interest and reading the replies.
Looks like you have done an excellent restoration... classic 'old skool' 

Edited May 3, 2020 by Philip R

[DaveL59]

1 hour ago, markse68 said:

Which cement @estwing? On the retaining ring? Mine had a tiny little dab of varnish to lock it but it span out really easily.

best to get a proper wrench for the purpose than risking force with 2 screwdrivers if just fingernails won't shift it. Not expensive and very useful to have if you are doing much with optics and other ring nuts like this one  

[markse68]

23 minutes ago, DaveL59 said:

best to get a proper wrench for the purpose than risking force with 2 screwdrivers if just fingernails won't shift it. Not expensive and very useful to have if you are doing much with optics and other ring nuts like this one  

Yes I was admiring that tool in your Tal-M thread- where did you get it Dave? Looks very useful

[DaveL59]

that one was off ebay as I've long since lost the one I used many moons ago when I repaired a Minolta 28-85 AF zoom that a friend had dropped, think I still have that lens somewhere with my 9000. There's quite a few versions of these, straight and bent pins depending on what you need, something like this one

https://www.ebay.co.uk/itm/PRO-STAINLESS-STEEL-DSLR-CAMERA-LENS-REPAIR-KIT-SPANNER-WRENCH-OPEN-TOOL-FADDISH/383419374209?hash=item5945935a81:g:l4UAAOSwXIheRS-E

There's much more expensive types that the real pro's use I expect but this type works pretty well, just set the right width and secure the bolts and recheck and then locate in the slots carefully and ease the retaining ring gently in the required direction.

I see the bay prices all seem to have gone up of late, side effect of the global mess I suppose, think I paid around £7 for mine. Still, I'd put it this way - you only have to slip once and scratch a lens and then one of these seem like a real bargain  I preferred not to make that first slip  

 

 

[johninderby]

Plenty to choose from on Amazon.

https://www.amazon.co.uk/s?k=dslr+spanner+wrench&rh=p_76%3A419158031&dc&qid=1588517516&rnid=419157031&ref=sr_nr_p_76_1

[markse68]

16 hours ago, DaveL59 said:

Does look a nice scope now you've recovered the lens, paint's not bad on it either, just the EP's and mount needs sorting. I'm part way through restoring one on the TAL reflectors, full repaint, hopefully it'll look good once done, spent more on paint than for the scope!

If I had a second time round  I’d become a paint manufacturer or a trbologist- have you seen the price of watch oil! 😉

Its a bit scruffy tbh but not too far gone- perfect for me so I’ll not be improving it’s appearance beyond functional stuff. Me and new things don’t really mix- that first scratch or chip is too heartbreaking. I’m more into wabi-sabi, far less stressful. You should see my car 😂

[DaveL59]

lol my car is 20YO I've only ever bought one new and since all S/H, much better value, tho downside is its heavy on fuel, not helped by a heavy right foot  

I do know what you mean though, I preference the older gear that can be refreshed a little to get something very usable and will last, hence my older TAL's  The odd little scuff in use isn't such a problem so long as it works, will have to see how precious I become once the little TAL has been restored tho, can see me wearing silk gloves to handle it  

[Stu]

Fantastic job @markse68! I was a bit confused when I saw the thread, I thought it was going back! Sounds like it was well worth sorting out though and you have given it a new lease of life. You are far braver than I am, taking it to pieces. My focuser could probably do with the same treatment, but I opted for a helical focuser on the diagonal as an easier option.k

Do get yourself a diagonal, far easier that way. I believe the rear thread is M44 so it is easy enough to fit an adaptor to take other kit. I have a T2 thread on mine and fitted a Clicklock so it is easier to use, although this take up a bit of inwards focus. Might replace it with a 1.25” as that’s all you need really.