unknown make vintage 3 inch scope

[DaveL59]

thinking more on the lens cell in this scope. Outer is brass with an inner ally (probably) front ring that are somehow secured together. Then the lens goes in and another ally tube inserted forms the rear lens ring. Now it's a tight fit into the brass and purely held by friction since it moves with some efforts twisting and pulling but doesn't come away easy.

On thermal coefficients I wonder if cooling the cell might encourage the ally to shrink a touch more than the brass and perhaps allow easier separation of the parts.

Aluminum

21 - 24

Brass

18 - 19

Just might work, maybe. Will pop it into the fridge for an hour or so later on and see if it makes a difference - if I can make room for it of course  

Edited July 18, 2020 by DaveL59

[Roy Challen]

3 minutes ago, DaveL59 said:

 

Just might work, maybe. Will pop it into the fridge for an hour or so later on and see if it makes a difference - if I can make room for it of course  

😀, Last night; Mrs C says: "There's no room left in the freezer". Me: "Hand me those tubs of ice cream".

[DaveL59]

so some success, in the fridge for a good while, nice and cold. Refit into the OTA so I could use the securing screw to hold it. Was still tight going into the OTA tho even with that at room temps. Still quite tight but gentle rocking the shield and it edged it's way to freedom. 20 mins later and...

Seems the lower inner tube section was glued into place so something I may have to consider when I refit, or tap a small hole and use a screw instead, likely the latter to make future maintenance a bit easier is my thinking. Explains why it was so stubborn to remove even tho the glue wasn't bonding to both parts any more. The mist on the lens is just condensation after around 1.5 hours in the fridge then going into a warm room with the humidity we have today.

So the lens, seems it is 76.8mm diameter and 13.3 thick at the edge, cemented doublet. As you can see it is edge blackened as well tho doesn't appear to be coated, probably the norm back when this was made. Took the opportunity to black out the spall using a carbon black paint pen, should improve contrast till a replacement is found.

Will now clean off the old glue and see how well the tubes then fit and put it all back together again. Once the paint has fully dried so I can clean the lens I may give it a quick test in the garden and another run at the planets tonight

 

[Guest]

What do you think caused the lens to break, did something internally fall against it or was it external pressure on the OTA? 

[DaveL59]

13 minutes ago, merlin100 said:

What do you think caused the lens to break, did something internally fall against it or was it external pressure on the OTA? 

I was working the lens cell to separate the inner tube and the lens became loose. Unfortunately it tilted as I turned the tube to try tease it further and the edge of the lens against the tube wall was likely too much and a chunk pinged away. Of course while rocking the outer tube side to side tiny amounts likely helped that as well. About to post pics of the cell tubes, the lens may well have found the lip which would have given it space to tilt.

edit: in fact the edge is visible in the pics above. The wide silver raised ring is where the lens sits and the inner tube presses home up to that point to hold it in place.

Edited July 18, 2020 by DaveL59

[DaveL59]

Cleaned off the old glue and the to parts are still a very snug fit tho do come apart slightly easier now. Looking into the cell fully assembled, the lip that holds the lens in place is very narrow. Maximising the aperture I expect

From the OTA end

and the dew shield end

At least I can reassemble as-is and be comfortable that it won't suddenly come apart unless I'm yanking on the dew shield while I decide on which way to secure the parts in the future. A small m2 brass countersunk I think would work well and should eventually age to blend into the aged brass.

 

[DaveL59]

So from the story so far...

It seems that while the lens fail was a disaster and I felt totally gutted at the time, it wasn't a complete disaster and the scope is in fact still quite usable. I do hope to source a replacement lens at some stage but it seems an 80mm will be too large and mean some mods that could change the look of the scope quite a bit. A 75mm would likely drop out or down the OTA unless I find a way to add to the lens retaining lip.

The ideal/easy solution would perhaps be to scavenge a battered Prinz 660 for the objective as that's a 76mm if I recall correctly... So I'll be keeping my out for one if I can find one at a reasonable price. Anyone got one they'd part with to be broken up I wonder?  

Meantime, back to thinking about restoration options on this lovely old scope 🙂 

Edited July 18, 2020 by DaveL59

[DaveL59]

Gave the leather a clean and feed and added some felt under those metal capping plates so they don't do any damage. The wood base has raw leather in the tube cut-outs which seems to work ok but now the scope turns more easily. Refitted the ancient Prinz finder scope and just been out and aligned it. It ain't great but at least it's something till I sort an alternate. With the damaged objective lens section blacked out the image is very good, you'd never know through the eyepiece  

Of course now it's out and ready to play the southern horizon is all clouds where the planets would rise (red squiggle) and traverse before I lose them to the oak tree in the south, that dreaded cloud god must've heard me saying earlier that I'd test this one out again tonight 🙄

NNW was heavy cloud earlier but seems to be moving so just might get lucky on Neowise again, time will tell...

 

Edited July 18, 2020 by DaveL59

[DaveL59]

ho hum, got a quick look at jupiter, clearly saw 2 moons and perhaps a third closer in with the old gal. Then cloud faded everything and more coming across, so packed it in for the night. Zero chance of Neowise tonight either, much heavier cloud to the north and pretty mottled all over so nothing much visible other than the odd star just peeking briefly thru small gaps to tease.

Still, feels like a successful day fettling this one so can't complain too much 🙂 

Edited July 18, 2020 by DaveL59

[DaveL59]

Decided it might be smart to secure the lens cell even tho I don't have a suitable brass countersunk at the moment, since they do rotate fairly easily, better safe and all that. So drilled and tapped for M2 and countersunk the brass side a little. I'll order some M2x6mm countersunk brass screws and finish the job later on.

The screw that holds the cell to the body could well be an older imperial thread, since the M2 fits, seems to hold but is a touch loose perhaps. That original screw doesn't seem to fit the M2 thread. Pity as I was thinking to make that brass too, as well as replace the one holding the focuser which is a longer M4 ish size.

While fiddling, decided to compare the brass eyepiece with the 1.25-inch ones I have, so sat the baby NatGeo 76/350 on the table and swapped them around. Luckily I have a 1.25-0.965 adaptor which made that easy. Seems to give an equivalent view as the TAL 25mm mk2 plossl just a touch narrower, but maybe not as much as the vixen 20mm compared the the TAL 25mm.

So I guess that old brass plossl (at a guess, not taken it apart yet) is around the 23-25mm mark, performs very nicely as well as being very nicely made. The more I play about with this old scope the more I'm liking it 😄 

[MarkAR]

The old brass one is quite possibly a BA thread.

[DaveL59]

5 minutes ago, MarkAR said:

The old brass one is quite possibly a BA thread.

yep am thinking that too, tho I don't have any BA taps these days and not one that small when I did as those were for car repairs so long since retired and disposed (foolish boy!). I may see how an M2 will hold and if not re-tap to m2.5 or M3 if I can source suitable screws, M3 countersunk have a deeper taper so may not sit well, don't want to lose threads off the inner tube as it's not that thick. On the OTA a dome head would work as it'd still sit below the leather surface, could go brass to highlight or black to blend and disappear I guess. For the shield defo brass so it fits with its surroundings.

[DaveL59]

This morning the postie dropped a couple things off:

Many thanks Roy for the 0,965 eyepieces and diagonal which will give the scope a degree of range of magnification without modifications. Well I will need to add a lock screw to the fine-focus mechanism but I'll organise a brass thumbscrew for that so it looks in keeping with the vintage 🙂 

The Vivitar lens cap is metal, felt lined on the inner lip and a perfect fit over the brass dew shield, result!

Lastly the M2 CSK brass screws - one needed to secure the lens cell parts together. Hopefully it'll age to blend in, or I'll maybe clean and polish up the dew shield to bring it back to its former glory.

 

[DaveL59]

so while I'm on "light duties" I thought I'd have a go to age the brass screw head. First try was malt vinegar and salt which had a little effect but seemed to not make much of a change after a few hours in the mix. Perhaps it might if left long enough. Should mention first step was soak in acetone to remove any finish protector. Certainly some effect as the threads turned pink, not the effect I was looking for tho.

Then I tried some balsamic vinegar and salt and even heating on the gas flame and hot dipping it. Some effect but not very dark. Read a tip that mentioned flux, of course now I want it I can't find the plumbers flux but I do have a flux pen for electronics work, so try that and see... has made a change but still not quite what I'm looking for:

I also swapped out the small steel CSK screw in the leather section for new brass, the M2 holds perfectly tho I might get a M2 cheese/pan head for this one later on.

Interested to hear any other thoughts on ageing/patina on new brass. Meantime I've another screw head undergoing just the flux treatment which I'll let age over a day or so and see how it does.

[DaveL59]

Gave the diagonal and eyepieces a wee daytime test now there's a bit of sun lighting up the distant tree branches. For sure very dim at 6 and 4mm but was able to make out what I was looking at. Nice clear image with the H20 and the MA40/original brass. Went from a branch and leaves to a leaf or 2 filling the FoV. Nice thing was the small eyepieces and diagonal don't seem to cause the fine focus to slip but the MA40 and original brass do of course, being much heavier and taller. I do think I'll need to fit a lock screw for the fine focus so I can re-lock the diagonal without losing focus and of course it'll be a touch fiddly to get the fine focus as that'll rotate the diagonal but it is what it is... Alternate might be to add a means to rack the drawtube without adding a rack to it but that seems too much faff.

Original brass plossl

and one of the smaller EPs

 

Am considering what to do with the finder, strip the paint on the foot and heat to apply a brassing effect (brass wire brush method) and re-paint the finder itself in black, perhaps.

 

[DaveL59]

so feeling a bit more able today and sticking with the light duties theme, decided I'd drill and tap the M3 hole for the fine focus lock thumb screw and also another in the diagonal so the eyepieces can be clamped - original for the diagonal was lost and the original threaded hole wasn't holding the screw as the first part of the thread was damaged. Small pilot hole then drill out to 2.5mm and hand tap and...

Wow tapping that brass with an M3 was surprised how squeaky it went even with a drop of oil! Here's the result, with the M3x8mm thumb screws that arrived the other day. Not quite a match but they can be aged. I so need to get a pillar drill if I'm going to be doing a lot of this tho as both are at a little of an angle but what the heck, not bad for hand-holding the drill and part and it does work which was the object of the exercise 🙂 (well the fine focus one will do eventually that is lol)

So nearly there but... on the drawtube the knurled part snags that silvered ring before it can go far enough. Should've been braver and drilled closer to the edge, maybe. But no worries, I've ordered some M3x16mm black nylon until I can sort some longer brass ones which it looks like I'd have to order via Ali since nobody in the UK seems to list them at the moment. Likely I'll fill that redundant hole later on too.

I did consider some vintage spark plug terminal nuts with a nylon screw glued in as they are a closer match to the original brass/nylon one on the focuser but those seem to be M4...

Being only 5mm between the silver ring and the edge I wasn't so keen to run a M4 thread there at this stage. Wonder if I can use that idea tho and re-work the nylon screw to reduce M4 down to M3 below the nut and not have it shred while running a regular die over it or  it just snap off in use?

I've also got some brass pan-head's ordered to replace the 2 screws on the OTA that are currently CSK, so they fill the hole in the leather a little better.

Still experimenting with ageing the screw head, acetone and heat in the gas flame to remove any lacquer and then I've inserted the screw into some tin foil, tape on the thread so it doesn't fall in and sat that over the top of a small bottle with malt vinegar in it. Leave for as long as necessary and it does seem to be gradually ageing the finish. Seems the acidity of the fumes is more effective than immersion, will show results if I succeed.

Dismantling the diagonal while working on that new tapped hole, discovered that it's a prism not a mirror which I hadn't realised the old 60's Japanese scopes came with. I guess that's handy though as it won't have deteriorated over all these years, very neat.

Edited July 28, 2020 by DaveL59

[MarkAR]

32 minutes ago, DaveL59 said:

the knurled part snags that silvered ring before it can go far enough

Maybe file a chamfer on the knurled bit thats in the way. 

[DaveL59]

1 minute ago, MarkAR said:

Maybe file a chamfer on the knurled bit thats in the way. 

Had thought that, or even grind into the silver ring to let it clear, but I think better to get a replacement with longer threaded section as there will be less to grip once clamped in a further 3mm. Not so bad now but on a cold night... 

There is a larger M3 tapped thumb wheel I can get from the UK, 15mm dia which might work ok with a nylon M3 screw inserted:

Kinda baulked at the £5 plus postage cost tho 😉 Could order a pack of 4 of this type for less than half the price and have spares

[DaveL59]

decided what the heck and mounted one in the drill chuck and ran it holding a file against the knurled section. Elf and safety would've been unimpressed but...

Result, thanks Mark for that suggestion, stirred me to try it having dismissed the idea when I though of it earlier so you saying the same added reinforcement and saves having to order a replacement 🙂

Fine focus now locks when I need it, I'll look at ageing the brass at some stage depending on the experimental results with the M2 csk screw head.

 

Hmmm looking at the pic, decided to try a different mod with a round file:

That's much better 🙂 

Edited July 28, 2020 by DaveL59

[MarkAR]

Second ones a winner. 

Was going to say if you need a one off made I can muck around on my lathe. Just let me know dimensions.

[DaveL59]

1 minute ago, MarkAR said:

Second ones a winner. 

Was going to say if you need a one off made I can muck around on my lathe. Just let me know dimensions.

thanks Mark, yep second one is more in the original style, just needs ageing a bit now. Was wary of trying it in a hand drill but it worked out ok in the end and no bits or files went flying 😉 

[DaveL59]

thought I'd report back on the ageing process (of brass bits that is)

Given this scope is vintage the bright shiny new screws really don't meld with the rest so having read around the web I've tried a couple methods but this one was what worked reasonably well for me.

You'll need:

• Acetone
• Malt vinegar (or cider vinegar)
• Suitable container
• Bowl to for a water bath
• fine grit emery cloth
• tin foil and tape

First up, soak the component/section with acetone for a while to soften/remove any protective coating, 30 mins say. Then gently rub down with the emery paper to remove any residue. Dip the part in vinegar and remove. Now rather than faff with making holes in the lid and screwing the parts into them I just went with a bit of tin foil folded and pushed the screw thread through, tape on the thread to hold them so they don't drop into the jar/vinegar while curing, like so...

Then pour some vinegar into the jar and pop the foil cap holding the screws on top.

Pour some hot water into the "bain marie" and leave for a long while, refresh the hot water every now and again. The idea here is the fumes from the vinegar act to age the exposed brass and heating should improve the fume rate.

Next morning the result:

Rinsed under the tap and rubbed with fingers and then dried off and fitted to the scope:

Quite a difference to the shiny non-aged brass that's also pictured and to my eye looks very good indeed, very pleased with the results of this little experiment 🙂 

 

[DaveL59]

today received these in the post

The brass pan-heads do improve the look against the leather I think 🙂 

The Eyepiece gives a very nice image, kinda completes the range for this one being I now have MA40, Original 25/20 brass plossl and H20 HM12.5, HM6 and Or4, no need for a barlow I'd say 🙂

Shame it didn't have a case but I'll sort something later on.

Looks like the finder was threaded for M5 but PO had used some non-metric size nylon screws that were hard to move. Direct swap and now easy to adjust and also release the finder shoe for removal. Yesterday I'd tried paint stripper on the bracket but hardly made any impression. Guess I'll need to sand it and then give it another go so I can get back to white metal and try the brass buffer treatment...

[DaveL59]

So tonight had a nice view of Jupiter+4 moons and Saturn as it popped out from behind branches, using the old 3-inch vintage scope and trying out a few eyepiece. H20, H12, HM6 and OR4, all gave nice views, think I could just about make out the division in the rings as well as some belt detail on Jupiter. Decided to then switch to 1.25-inch since I now have a 1.25 to 0.965 adaptor, Fullerscope 12mm and a circle-T OR9 on the same scope. Again nice views, a bit clearer than the 0.965 EPs but all worked well. Popped the TAL 2x Lanthanum barlow into the mix and still good views with the 12 and 9mm's.

Must say focus with a drawtube is real fiddly and the rig certainly had the wobbles while doing adjustments, tho probably not much worse than a modern manual focuser in terms of inducing wobble. EQ5 on the ally tripod with legs extended so I could see over the fence likely didn't help. Might have to consider getting a pier extension for the mount if that'd make things more stable. I did note that freeing the drawtube lock screw and moving the tube can cause a shift of view until tightened back up so I guess there's some play but then this is quite an old scope now 😉 

All in all pretty pleased, the old scope can still show very nicely and with the range of 0.965 inch eyepieces works really well. Not sure how much difference it'll have made but while I had the diagonal and eyepieces stripped down for cleaning I also blacked the ground edges on the glass, prism included. Simple black sharpie marker was used for that which usefully adds no thickness compared to painting as some of those tiny eyepiece lenses are a very snug fit not to mention real fiddly to refit.

[DaveL59]

After a long time since looking at this one, I thought I'd have a look at replacing the finder shoe so I can use the TAL finder in a Synta type holder. So pop the drawtube out and pliers in the tube to hold the nut while I undo the screw. The shoe didn't drop away so I teased it up with the screwdriver to be left with this

Drat! That's disappointing given the replacement is smaller in footprint. The old show had been glued as well as a single screw/nut to secure it.

Looks like I'll either need to get some leatherette and fill that gap, re-cover the entire OTA or leave this in place and mount the Synta-type foot elsewhere on the OTA. Oh well, nice idea but gonna be some faff then. The old finder does work ok so maybe I'll leave this and just see if I can progress the idea of stripping the grey paint and brassing it then. The other idea on the Synta style shoe was to make it easy to swap the DIY Starsense carrier onto this scope when I wanted to so maybe adding it offset to this shoe would work out ok, can then use a RDF or starsense alongside the optical finder as required.

While I had the focuser out I laid some sticky-back teflon tape around the inner rim of the 2 collars the drawtube runs in. Has taken out the slop and made it slide smoothly with a little drag in the movement without the metal on metal screech which is a good thing, esp on those very quiet late nights 🙂 

Edited November 2, 2020 by DaveL59