TAL-M refurb

[sloz1664]

Is the focuser a R&P or Craford?

Steve

[DaveL59]

Hi Steve

for the TAL-M the focuser/finder is an integrated unit with a helical focus control:

The finder slides back into the body for use and there's a diagonal mirror that it puts into the path between the eyepiece and secondary. Very neat and quite usable. Looking at it again though I'm thinking my idea of tapping a 4mm hole might not fly as it'd need to be in the knurled section. Back to the drawing board on that idea then lol it just seems maybe easier than trying to chamfer the edge of the 25mm eyepiece barren to slip easier by the spring you can see here under the lip:

A simple solution to securing, no fiddling with locking screws, but having flattened it more into the sides for the TAL-1 EP's there's a risk of an EP dropping out if careless when swinging the OTA. Am thinking forward a bit for if this one goes to my daughter and her little one to use, hence me adapting the pier before I started the painting  

 

[DaveL59]

getting dark and threatening here  Hope I can get all the trips to the shed to finish the OTA before it tips down or I expect it'll be wet feet for me again. 

[DaveL59]

yep, just as I walked back from giving another coat a few drops then more. A few claps of thunder just now too brought kitty who was zzz in the conservatory running in for comfort bless him. Hopefully it'll be a brief shower as the wind does seem to be driving the clouds eastward.

So time to start looking at the next component, the ALT-AZ head. An L-shaped unit with built-in counterweight and OTA carrier all-in-one.

The tube rings have these plastic buttons to bear on the tube, allows it to be rotated but I think too they didn't help the paint, the scarring once started was just expanded by these I'd say. I did put a couple felt pads on for while I was using it to see how that worked and it did help so the plan will be to remove the plastic pegs and felt line them once the respray is finished.

Underside shows where the pier knuckle goes, making it possible to use this setup as an EQ/wedge or ALT-AZ depending on preference. In its past life the knuckle bolt was loose so of course this meant the head body was hitting the pillar, damaging the paint quite a bit. No real damage other than the paint though, that old russian battleship build quality takes some beating  

 

[DaveL59]

ok so a longer post with pics of disassembly in case its useful to someone else (me!) later. I didn't with the previous posts as those parts are all pretty simple and obvious being just a couple screws and you're done. So here goes...

First up how to open up the L-shaped ALT-AZ unit so we can strip out the controls. Well there's the 4 screws underneath as per above pics but that ain't gonna do it, you'll see why in a few. The first step we need to do is to remove the OTA carrier which has a screw per corner. You need to undo the locking screw so the carrier rotates and then undo each screw as you rotate the carrier to bring them into view. Perhaps worth mentioning here for those unfamiliar with this baby scope, the short black knob is the Slo-Mo control, the longer one is the locking screw. It is NOT a lever and as noted in another article I'd read ages ago, yank on it like it is and you'll likely shear something off and render the controls useless unless you can machine up a suitable replacement.

So with the ALT Slo-Mo controls now exposed we need to strip those down to be able to remove the swivel plate the OTA carrier attached to. As indicated in red, the locking screw on mine is missing a circlip to prevent accidental unscrewing which I'll find a replacement for later, in fact the Slo-mo screw is too in this case.

So a fairly simple case then of remove circlips, unscrew the controls and remove, then remove the spring. Then you've the fun of removing the spring-clip that prevents the arm falling off. Proper pliers may help a lot here, but I used some fine-nose right-angle ones to tease it open and a screwdriver to lever it, then teased it up and off  

So now we remove the retaining ring that clamps this plate onto the plain bearing on which it rotates. Don't forget to undo the locking set-screw first tho! The ring with be screwed on fairly tight as this sets the loading on the bearing, too loose and the ALT axle will be wobbly

 

[DaveL59]

Now we have the ALT plate removed revealing the 2 hidden screws that still hold the base panel on.

and the slo-mo parts in a box for safe-keeping

So off with the base plate then and... there's the AZ controls and counterweight 

counterweight removed - simply unscrew the knob in the middle of the top plate  

Just as the ALT control we remove the circlips and spring and unscrew the knobs. The set-screw indicated locks the bearing collar, unfortunately it's not wanting to move so the swivel may need to remain in-situ while the unit is sanded and painted, not ideal. May try some heat later, being very careful of course as there's grease present on the bearing faces.

On this one, after teasing out the retaining spring clip the arm wouldn't quite slide off, it needed a little persuading, gentle open the locking collar and it comes off easily

 

 

 

Edited May 1, 2020 by DaveL59

[DaveL59]

And there we have it, the ALT-AZ body stripped and ready for degrease, prep and paint  

I'll strip the black OTA carrier later as I'm working through the white smooth paint parts at this stage. I've not figured out how to remove that black collar you can see, its the screw threading insert for the slo-mo control and doesn't seem to have any simple means to remove it, so I plan to leave it there and mask it off at this point.

Time for a coffee I think and some biccies too!

Edited May 1, 2020 by DaveL59

[DaveL59]

meantime, the OTA's had around 6 or 7 coats during today so it can now sit suspended to start to cure before being moved into the airing cupboard tomorrow to finish curing. That old spare length of plastic pipe that its suspending on has been very useful so far, made rotating the tubes very easy by just turning the pipe as I worked, tho I can't say my fingers didn't get some overspray as I'm sure has my hair  

Thinks I got a reasonable flat finish too, he says tempting fate. Will know tomorrow when its ready to be handled I guess...

[DaveL59]

so midday I retrieved the OTA from the shed, paint hard but a few pin-points raised on the surface here and there. Not orange peel but overall a nice smooth glossy finish, I can live with that. Can always give it a light run down and throw a layer over it later if it does bother me. Either way it looks 100x better than the paint scarred OTA I started with, so its now in the airing cupboard with the other bits to fully cure off  

Onwards then, sand down the head casings and then degrease wipe and mask. But first now its sunny, see if I can figure that black thread insert. Given the excellent engineering that went into making these I was figuring perhaps a 3mm grub screw down that threaded hole and the insert screws in and is locked in place.

Nope  Must be a way but I sure can't see it, the hole is rough at the bottom and stops short of the black insert, solder? Oh well, on with plan-A then.

So anyways, got it all sanded and masked, didn't take it back to bare metal so will see how that turns out lol. Yep that's duct tape as well as masking tape, bad man! but heck it sticks well where I need it to unlike the masking tape. Any residual glue won't affect as it'll not be on the bearing faces but will get cleaned off first anyways 😛 

So into the shed to spray first coat then.... and as I was about to hit the spray button... OOPS! I'd forgot to mask that black insert, quickly fixed tho  

under that kitchen paper is a small lazy susan by the way. Dead handy to be able to rotate the part to get round all sides and not have to touch wet paint.

After this then its just the OTA carrier and rings and then the focuser which will need the lens and mirror cleaned as well as paint freshening up. Getting there, assuming I can remember how to put it all back together in a week or so  

Edited May 2, 2020 by DaveL59

[DaveL59]

thought I'd check in on the smoking cupboard. oops curing cupboard AKA airing cupboard. Looks like the bits are setting nicely to a smooth hard white. Even the baked bits that I turned biscuit coloured are looking good after they'd been given a spritz of fresh white to retrieve my mistake  

The newly painted OTA at the top as too tall for the lower shelf, plenty room for the ALT-AZ bits once they're ready to move to curing tomorrow. One more coat on those parts and I think will take a break from all of this till Monday, need a break from sniffing paint I think  

 

[markse68]

23 hours ago, DaveL59 said:

But first now its sunny, see if I can figure that black thread insert. Given the excellent engineering that went into making these I was figuring perhaps a 3mm grub screw down that threaded hole and the insert screws in and is locked in place.

Nope  Must be a way but I sure can't see it, the hole is rough at the bottom and stops short of the black insert, solder? Oh well, on with plan-A then.

Isn’t that just the screw boss for attaching the cover Dave? Looks like that insert is either cast in place or a press fit? 

Tal stuff was really nicely engineered wasn’t it- particularly given their cost back then.  Might have to keep an eye open for one of these quirky little scopes now you’ve shown us what’s inside 😉 love that finder/focuser ingenuity 😍

[DaveL59]

Hi Mark

 

yep that's the thread for the cover retaining screw. Was just thinking if the clever russian maker did what I'd have done and tapped it right through and banged in a set-screw to hold that threaded insert.

As to press fit etc, I wondered about that too Mark, for sure its tightly secured and I'm not planning to force anything and wreck it given its a key part of the AZ adjustment. I did have a little try with a circlip on the end of the control knob to see if it'd just unscrew on the basis it might have screwed into place, but it didn't budge. Since it is a different finish, anodized perhaps it must have gone in after the main casing was painted, so press or screw fitting seems the most likely. Should check if the threaded insert is steel in which case maybe heating the casing and pushing a cooled steel inset was how they did it. Simple and effective whichever it was  

The only negative I've read on the TAL-M was around the bearing, plain metal faces pressing against each other. Not that it doesn't work, just if the ring clamp nuts aren't tight enough you get a little play that results in a slight rocking. Mine was like that when I got it, just slightly, but an easy fix which I did soon after buying it. Not bad though for a 26YO scope if that and the paint are the only things wrong with it. Somehow I doubt my hardly used 5YO SW130 will be that good in 20 years time but I bet the TAL's will still be in great shape other than maybe the paint. That'll be someone else's problem by then tho  

Edited May 3, 2020 by DaveL59

[DaveL59]

ok so picking this thread up again, yesterday I noted the L-shaped ALT-AZ head had some sags in the paint on the vertical edge  So sand things back and flat it and then redo, seemed to have enough paint in the spray can, or so I thought. Nope ran out on first light coat. Oh well so this part I cannot finish yet - seems the local DIY store is out of hammerite smooth white at the moment so hopefully I can pick up another can later in the week when they might get some stock in.

Oh well... guess I'll look at the OTA carrier instead then.

 

 

Edited May 5, 2020 by DaveL59

[DaveL59]

The OTA carrier is a pretty simple affair, a block that bolts to the ALT bearing plate and 2 half-rings that clamp the tube into place. Now I've noticed in some ads that the OTA rings can get broken, since they have 2 holes for a plastic buttons in them I guess that can be a weak point. I've decided those plastic buttons have to go, since they bear directly on the OTA and the paint and so tear the paint up when turning the OTA to adjust the focuser position when viewing.

First up then, remove the hinge pins so we can remove the rings

Now I removed the plastic pegs, cutting away the back and then teasing them out with a screwdriver. Drilling them might have been quicker but I was too lazy to get up lol. Also removed from the OTA carrier base hence those holes. I'll use felt strips in their place when I reassemble.

Now for the ring clamp thumbscrews. There's a screw in the end of the threaded section to prevent the thumbscrew from being unwound off the end and dropped in the dark, so unscrew the retaining screw and then the thumbscrew, nice and simple. Then we want to remove the bolt section, but this time there's no screw head on either end of the retaining pin. Hmmm ok, so after trying lightly I found that these simply tap out with a suitable drift, in my case the tip of the thin pliers tapped with that big screwdriver  

leaving us the clamp screws for the tube rings... ( I do have them all, just not in the pic)

And there we are, OTA carrier stripped  and ready to be prepped and painted.

Am thinking a nylon washer under each thumbscrew might be a good option to protect the paint when I reassemble this, or even just a plain stainless washer, one to consider later on. Would prefer they don't look like this after taking the time to refurb it all.

Edited May 5, 2020 by DaveL59

[DaveL59]

After sanding I looked closer at that silver ring from the clamp screws, they're indented slightly, machined that was I wonder, or just years of tightening up the tumbscrews, hmmm.

Anyway, decided I've had enough of breathing spray paint so I went with brush applied hammerite black hammered finish on these bits, hopefully one light coat will be enough and give a nice finish, will see once its cured I guess  I know I'll need to skim the edges of the hinge and its counterpart as they were snug before I started, a bridge to cross once the paint is fully set.

[DaveL59]

checking in on the hand-painted bits, so far looking ok. A couple corners where paint got a little thick and sagged plus brush strokes on the sides. Downside of hand painting I guess. So sanded that and added a second light coat, hopefully will improve the look a little. The rings came out nice tho as did the bed where the OTA sits, just faintly showing the machining under the hammerite hammered finish which I quite like.

Now then, on to the last part that needs working on, the focuser. Never found a guide tho I didn't look too hard, so lets just crack on and step into the unknown a little, can't be that hard can it?  

Now this little beauty uses a single helical focuser and regular eyepiece (well the older TAL 32mm type ones in fact) to double duty as finder and target viewing through the main OTA by interrupting the light path and placing a mirror diagonal to divert the view through the finder. Hope I can get the diagonal aligned ok after I reassemble it all!

Underneath you can see how the drawtube is handled to limit its motion and keep its orientation.

Indicated are the locating pin (screw) that slides in the channel, the ball bearing under a spring that acts as a detent at the extremes of the drawtube's movement, and a little set screw under the front lens cell. The lens cell is retained by a regular ring that screws in at the front (seen in first pic) and once the set screw is slackened/removed the cell can be teased out. I'm sure that black collar should be possible to unscrew but it didn't seem to want to play and I can paint it in situ anyways so I elected not to force things.

My one thought on this surface is that (if you recall the pic of it) the OTA is open along a big chunk of the focuser body and it ain't exactly flat black. I'll likely give that a coat of something to improve the light-killing properties after the main top coat of paint has cured. Flat matt black enamel or blackboard paint perhaps.

Back to dismantling, removing the locating screw and the spring and ball bearing, being careful not to lose it bouncing off the desk and disappearing... yeah I forgot to put a towel under it all before starting this time lol. Withdrawing the drawtube we now see the aperture and the diagonal that gets the finder to work under the eyepiece and the detents for that ball bearing to catch into, clever bit of design, no?

With the drawtube removed, lets now get the helical focuser out too. Here we back off a small set screw in the side of the barrel and simply unscrew the helical and its off. 

But I also want to remove the section it screws into, since it has a different finish to the main body. In fact this part is the other half of the helical so in fact might have been removed in one with a strap wrench, now I've seen how its put together. Anyways, inside the tube you can see 2 holes in the rim, so pin wrench set to the right opening and unscrew it from the main body.

Will have a measure later of that thread into the main body, wonder if a regular 1.25-inch low profile helical would screw right in in its place? Could make for a handy update down the road, perhaps. Oh I should mention here, that little set screw retaining the helical inner tube - do not tighten it right up when reassembling as it'll drag on the inner tube and feel horrible in use. It only needs screwing in enough to stop the focuser being unscrewed too far to prevent accidental removal in use  I'll probably melt a drop of black wax in to secure it when I've finished assembly, just so it doesn't try to escape one day.

Now before I sand and paint that collar around the front lens, lets remove the diagonal and risk the faff or getting it all realigned later. Better safe and remove than risk ruining the diagonal during this process I think. After all, how hard can it be to realign, right...?

The back end of the drawtube looks like this

and there's 3 set screws in the sides holding the inner assembly in place (forgot to grab a pic, sorry). Looking vaguely familiar, much? You'll see why in a sec.

So back off the 3 set screws in the side and that inner can rotate and since its an assembly, so does the diagonal mirror of course. Now I did score a mark across the tube end first so I can replace it in the same orientation, hopefully that'll pay dividends later but I've a feeling it'll be an easy fix either way. Seems you need to back these little set screws a fair way and then, gently upending the tube onto your hand, out pops a little mirror assembly  Store this and the lens away safely while you work on the paint refresh, but here it is, TAL-M focuser dismantled and ready to refurb.

 

Love how neatly engineered this little scope is, a wee secondary mirror arrangement for the focuser/finder diagonal is genius. As is the simple way it can be adjusted - see the holes (indicated) in the rear screw thread on the body where the end cap goes? They align exactly for access to those set screws that retain the finder diagonal, so getting this back together and aligned should be pretty straightforward  

So I've now sanded the main body and lens ring and laid a light coat of black hammered by brush. Hopefully it'll look ok and not too brushy. Once dried, that's pretty much all the painting done! Tho I do need to redo the L-shaped ALT-AZ body, but that's stuck waiting for paint stock to arrive at the local DIY shop. The optical elements will get a clean as I come to the reassembly, the main mirror cell and secondary spider I'll review in due course but they looked fine when removed so may not need any attention at all.

Edited May 6, 2020 by DaveL59

[DaveL59]

Measuring the helical focuser outer thread before packing it away for safe keeping, seems its 31.8mm fine pitch. Wonder if the SVBONY or similar would fit directly in its place...

Its a thought but unlikely I'll pursue it, any swap would need enough in-focus to make regular 1.25-inch EP's work so would need to be pretty low profile I think.

Will say I'm quite happy with the TAL unit as it works, is smooth and of course its OEM, but you are limited to the older TAL 32mm eyepieces unless you use the barlow as regular 1.25-inch EPs don't reach focus - not enough in-focus being the issue. This of course renders both the finder and main scope useless sans-barlow. Luckily I now have the older 25mm plossl, two F15mm (Kelner I think) and the 3x barlow of the correct or original equipment for this scope so it ain't the end of the world  

[markse68]

That Plossl is pretty decent 👍

[DaveL59]

2 hours ago, markse68 said:

That Plossl is pretty decent 👍

thanks Mark, and yes it definitely is, I've an older 32mm bore 25mm plossl for this and also a type-2 and 2 of the more recent ones now which are 1.25-inch, the latter have different colour to the coatings, one that nice purple and the other greenish. In fact the TAL eyepieces form the bulk of my EP collection as you can see:

The LH F15 is the original one from the TAL-M, note the chamfer on the barrel compared to the 15 and 25 to its right.

I've a couple Vixen NPL (20 & 10mm) and then there's these

an old Meade MA40 0.956mm with an adapter to 1.25
and a couple noname kellners

All give pretty nice views and I do still have the SW ones that came with the SW130, and a plossl pair I bought for the NatGeo 76/350, again noname but were a big upgrade from the junk that came with that scope  

One day I may aspire to join the upper tier club but I'm quite happy with these really so not felt the need... so far...

Edited May 6, 2020 by DaveL59

[markse68]

Nice collection Dave! I narrowly missed out twice on the 42mm Kellner- how do you like that one? But I did get one of these 2” Siberia 50mm erfles which I think are really the same company as Tal- very similar looks anyway. It’s a beast and a very nice finder ep.

[DaveL59]

that K42 is lovely, gives really great images so was well pleased to land it. Have been tempted to go after one of those 2-inch erfle's that you have, I will admit, tho to use it I'd have to be doing acrobatics with the 100RS as I don't have a 2-inch diagonal

[DaveL59]

so, inspecting the OTA carrier and focuser, still brushy marks  At least the objective beauty ring did come out nice so won't need anything further  Yep that's a toothpick in the set screw hole to save me having to re-tap that one to clean up the threads after painting.

Now I have a plan, IF I can find it. Flat it back and give a coat with a paint pad... pretty sure it's somewhere, now where's that black hole gone hiding  

Local DIY got new some stock so I can redo the L-shaped ALT-AZ mount body too, which with these done will complete the painting works, finally!

[DaveL59]

so having re-prep'd the control head body and started to spritz it with paint, I thought I'd turn my attention to the OTA since its been curing several days now. Not totally happy with the prickly bits here and there in the paint but lets have a look at flocking it. Now I've a number of sheets of A4 size flock, not the "proper" astro stuff, but is it usable? Well it leaves around a 1CM gap between the edges if laid square on, but inclined it might work. Laying 3 sheets at this offset layout to test the idea gives a really nice dark inner indeed so could well be worth doing. But the inside of the TAL tube feels a bit greasy so it ain't gonna stick reliably then. I remember astrobaby said the same when she did the TAL-1 so seems a family trait then in the TAL line? Maybe its to snag the dust and pollen falling into the OTA and reduce the amount that gets onto the primary mirror?

Oh well, kinda shoulda de-greased the OTA inner before I'd started painting then  

While I come up with a plan-B (flock onto acetate sheet rolled and inserted in the OTA, probably) I decided to console myself with gently sanding the OTA's fresh paint to smooth off those annoying blemishes and start giving it a light refresh coat or 2 - heck it might as well come out of this looking $1m than not, well I guess more like $10  

Still not managed to locate the mysterious paint-pad eating black hole either, will have to nab one when am round at my Dad's in the next couple days to check/cut the grass...

[DaveL59]

been a few days, but after lots of frustration getting the L-shaped casing to get a nice even finish, I ended up sanding it back hard and getting it nice and flat, then rather than burn thru hammerite white spray, went with laying a few coats of grey primer and then smoothing and repeat, to get a better surface finish. So on with white hammerite smooth spray and several coats later...

at last, no sags in the paint and finish is pretty smooth too! Mind it was cooler too so maybe that helped a little  

So into the curing cupboard it went today with the rest of the parts and I'll wait for a week or so for it all to harden off.

Still to sand the focuser and OTA carrier and try a paint-pad to hopefully get a less brush-marked finish, when I obtain the pad I'll revisit that bit as it shouldn't take long - unless its a total fail in which case lots of sanding back to do lol

[DaveL59]

Having got a paint pad and cut it back to a suitable size, I flatted and went over the OTA carrier and focuser with high hopes the finish might be a bit flatter with less brush marks. It almost worked, but perhaps a colder day making the paint thicker (less than half left so that may also contribute) the finish isn't what I'd want on the finished assembly.

Downside is to get the hammered finish you need enough paint laid on and being multi-surface of course it gathers and runs/sags after you walk away to leave it to set. Oh well, gave it a go, but I think I'll be flatting this back and then going back with a hammerite smooth black spray which should hopefully give a better overall finish. Pity as I kinda liked the slightly hammered look for these parts rather than flat gloss.