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Hello

My brother picked up a an old 1995 Tal 1 Newtonian scope 2nd hand recently, using my standard plossel 1.25" eyepieces i cant achieve focus as there is not enough inward focus travel, the mirror appears to not have been moved, is there any way round this? i had an old tal x3 barlow but i unfortunately sold it. will this solve the problem? Any help appreciated.

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The Tal1 does have limited travel but when I had mine, I think it was a 97 or 98 , I had no problem focusing Vixen NPL  plossls. There was a problem focusing just about everything else especially anything with a built in barlow type element. Eventually I did a big makeover job on it and replaced the focuser with an item off a Celestron/Skywatcher 114mm scope. Not an easy job and the focuser was nothing special but it had the travel to focus just about anything which was a big improvement.

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thanks for advice Alfian, but i basically dont want to spend much time on it, will a Tal barlow if added then allow standad 1,25" plossel eyepieces to work? 

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the barlow should work, does on my Tal-M.

Alternatively moving the mirror cell up the tube using longer screws and springs would allow the standard EP to come to focus, if you do a search there's a few topics on that here and elsewhere. I tried this on the Tal-M and it worked fine, downside for me is the finder is built into the focuser body so that now won't come to focus with modern EP's, not figured a solution for both so far, but at least on the Tal-1 the finder is seperate I believe so won't be affected.

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just collected a 1995 tal-1 this evening, luckily it has the 15, 25 and 3x barlow. Sadly no original wood box but otherwise in pretty good shape. Assembled now but no chance to test it as true to form it's all cloud outside in every direction.

@Astroblagger, did you ever do the mirror shift? If not and you still have the scope then I'll update once I've had a chance to look at this one properly but that'll be sometime over the next month or so, probably.

My plan for this Tal-1 is to shift the mirror so it can use regular EP's and use the originals on the baby Tal-M I have, which will complete that scope other than the 32mm extension tube. Seems an easier solution than trying to figure how to adapt the built-in finder to work with newer EP's. I need to drop the mirror back to original location on the M and then test and once I'm happy it can get stripped down and repainted (or powder coated) etc and be stored in its wood box 🙂

I've so gotta stop collecting vintage optical gear!!! 5 scopes and 35+ airs of binos is getting a lot too much lol. Tho I'm quite pleased with the TAL collection, being a TAL-M, TAL-1 and TAL100RS with a range of EP's now at 42 (mk2), 25(mk1,2,3), 15(mk1,2), 9, 6.3mm and 2+3x barlows. Really hope I can resist if a Tal-2 comes up locally 😮

 

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Posted (edited)

I did it a while back to mine- I used alu spacers so I could  reuse same springs though I swapped the screws for Allen heads to make it easier not to slip and scratch it up collimating

Saw a really beautiful early Tal-2m at the Deutsches Museum Munich last week- no plastic on it anywhere- even the OTA cover cap and finder dew shield were turned aluminium 😍 Most seem to have plastic parts that I’ve seen on eBay 

17101F6B-B868-42D8-9A74-D8126FEB21C3.jpeg

6BF4946C-BAF3-4D7A-8CC2-C44B0A3D8C45.jpeg

7361897D-0994-496F-91BA-D47EE705E5C2.jpeg

Edited by markse68

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wow, very nice that one! This 1 has the plastic end cap intact, worst case if it breaks I'll source a nitrile bearing cap of suitable size like I did for the M. it's metal internally and a snug fit to the tube.

Nice mod, how far did you raise the mirror if I might ask?

For the M I obtained some 3d printer springs and raised that one 25mm ish, probably could have done with being a touch more but those parts may well work ok on the tal-1 once I revert the M back to original screws/springs.

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Haha I can’t actually remember- think they were 20mm long the posts but probably could have been 15. Now of course the 32mm og eps don’t reach focus 😂 But all my 1.25” eps focus now.

What are these nitrile caps you speak of?

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in this post I talked about the Tal-M

 

I got the nitrile bearing cap for the mirror end and used a modified pipe cap for the open end on that scope. Keeps the dust out and also closes any light leaks at the mirror end

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Thanks for the link- nice end caps and very interesting old thread 👍

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so having swapped the tal-M back to original mirror position, I've used the longer screws and springs I'd fitted on the tal-1 mirror cell and rough collimated. Tal-M now comes to focus fine with the tal-1 32mm bore EPs and gave nice views of the moon. The Tal-1 focused fine with regular 1.25 Ep's (tal and vixen) tho I think slightly longer screws might be better but will see how it goes 🙂

Only thing is the tal-1 EP's are very tight going into the tal-M focuser and impossible on its barlow. The tal-M 15mm has a taper at the end and seems slightly narrower bore, so thinks I'll have to mod these to reduce the bore a little and add a chamfer so they fit more easily.

All in a pretty good result I think, as I can leave the tal-M as original and it'll be a handy scope for popping in the car boot and for the grandaughter to look through. I plan to reverse the threaded insert in the pier so it can be used with just the lower section for her 😉

I guess now I know it'll all work the way I hoped it'll be time to strip both down and sort doing a refurb as time allows. Need to sort the finder on the tal-1 too as its focus is loose and rattles, as does the primary mirror I noticed when I had the cell out.

 

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Posted (edited)

thought I'd update. Ordered 60mm allen head bolts and 40mm setscrews to lift the mirror a bit more and also some longer springs with 1.5mm wire. Sadly the springs are way too stiff, well IMHO as I'd not want to overstress the threaded holes in the mirror carrier so I've ordered up some 40mmx8mm OD x 1.2mm wire ones which will be fitted when they arrive. The bolts are only threaded at the far end and when screwed all the way give a mirror lift of approx 30-31mm. Handy as that's around the sweet spot for the distance to lift I believe. The 40mm setscrews ideally could've been 5mm longer but I didn't find that length when ordering, they seem to do the job fine tho.

Parts ordered:
M4x60mm:
https://www.ebay.co.uk/itm/M4-M5-M6-M8-A2-STAINLESS-STEEL-ALLEN-BOLT-SOCKET-CAP-SCREWS-HEX-HEAD-DIN-912/221307549544?ssPageName=STRK%3AMEBIDX%3AIT&var=520187427009&_trksid=p2057872.m2749.l2649 

M4x40mm
https://www.ebay.co.uk/itm/M4-M5-M6-M8-A2-STAINLESS-STEEL-FLAT-POINT-GRUB-SCREWS-SOCKET-SET-SCREW-DIN-916/232246807222?ssPageName=STRK%3AMEBIDX%3AIT&var=531471400554&_trksid=p2057872.m2749.l2649

Springs:
40mmx8mmOD, 1.2mm wire 
https://www.ebay.co.uk/itm/Compression-Spring-8-20mm-Outer-Dia-10-50mm-Length-Stainless-Steel-Various-Sizes/283335191701?ssPageName=STRK%3AMEBIDX%3AIT&var=584260830435&_trksid=p2057872.m2749.l2649

Rough collimated which is fun when the mirror literally floats about (no springs) but got it reasonably ok for a quick test. Vixen 25mm I was able to focus on some treetops a couple hundred meters away with the rack extended most of the way out. On testing with a Vixen NPL 10mm, focus was a little under halfway raised and was easy to achieve, giving nice views of Saturn just now. Adding a regular 1.25 (tal) 2x Barlow worked fine too, so I feel it was a good result overall.

These particular screws will give the option to lift the mirror further up the tube, tho the setscrews will run out of usefulness if more than a few turns, so not really advisable. If I do need to be able to pull the mirror further back down the tube I can always cut the threaded section a bit longer to suit, luckily I have a tap and die set to do this with, but if you don't then maybe best to find bolts that are threaded on a greater length of the bolt than these ones.

I don't really think stronger springs will make much difference really as their main purpose is to keep the mirror fully raised vs the screw tension while collimating. The setscrews lock the adjustment and the combination of the pair of screws at each adjustment point is what keeps the mirror stable.

Will let you know how I get on with these 40mm springs once they arrive and post a pic of the setup once I've all the bits fitted :)

 

Edited by DaveL59
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So the springs arrived today and now installed in the mirror cell. They're quite stiff but not compressing them much since they are around the length needed to allow the mirror to float on them while adjusting collimation, which only needs a mm or two movement at each fixing point. Once the locking set screws are tightened the mirror doesn't seem to move at all so should be fine when handling or moving the scope about. Note that the springs fit into a recess on the end plate so some of the 40mm length is lost so you'll only really get a lift in the range of 28-32mm but that seems in the right zone to achieve focus.

Here's the completed assembly with the bits listed in prev post.

Tal-1 Mirror mod.jpg

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