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TAL 1 - EYEPIECE PROBLEM


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Hello everybody. I'm new to this (both stargazing and forums) and would really be grateful for some help.

I have bought a second hand Tal 1 telescope. It is my first telescope - It is an older telescope - 1994 and is slightly grey in colour (rather than white).

Unfortunately it didn't come with any eyepieces. The seller told me

that these would be very easy to get hold of.

Being a complete novice, I went out and bought a couple of Revelation 1.25" plossl eyepieces (12mm and 15mm).

I was so excited when I fitted the eyepieces and tried to use the telescope for the first time. Unfortunately the eyepieces do not bring the telescope into focus (they also feel slightly loose).

I have now 'Googled' this to try and find an answer. It appears that others have experienced this problem. I am now feeling slightly foolish for not doing a bit more 'homework' before I bought the telescope.

Is it possible to buy a conversion kit to either change the focuser or somehow reposition the mirror in the tube - or have I bought a complete load of rubbish ? I am so disappointed - any help /advice you can give me would be most welcome.

Thanks

Lumpnuts

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The seller was right and the eyepieces you have, 12mm and 15mm should fine in it.

I would guess that you need a small extender to move the eyepiece back. Any further details on where the problem is would be helpful. I am assuming that you cannot wind the eyepiece back enough to get a sharp focus.???

Did the scope come with a diagonal - it should have, but if not and you are looking along the scope then you will need a diagonal, which will add to the focal path.

The loseness may simply be expected, however there should be a small knurled screw on the side of the eyepiece holder to grip an eyepiece, sounds as if that isn't there. If you find the screw+thread size then an alternative can be found. A small alan headed screw would be OK.

If the eyepiece is literally far too small for the eyepiece holder then I suspect that you need a 2" to 1.25" reducer for the focuser, again this will move the eyepiece back so could be the problem.

I would suspect that it was sold because it was not used, and the reason for not being used was the loss of a couple of small bits.

Stick a location on as it may be possible to point you at somewhere useful, like a shop, or club.

By the way the scope is probably very good, just need to iron out the hiccups.

Edited by Capricorn
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Welcome to SGL :D.

If memory serves, the older TAL's don't use standard 1.25" eyepieces, they have their own slightly different size. Whilst that'll probably the looseness issue, you still should be able to bring the thing to focus. Your mirrors might be horribly out alignment which might be the problem. Have a search for 'collimation' and have a read.

HTH

Tony..

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do you mean the tal 1, or the tal alkor, as the tal 1 (in white) uses a 1.25 but the tal akor both gray and white used a funky sized eyepeice (i beleive they are the same as microscopes use but not 100%)

easy way to see is the tal alkor has a finder built into the focuser the tal 1 dose not

a diagonal shouldnt reallt be used as it is a newtonian but a eyepeice extender could be used to focus

some eyepeices you see need more focus travel than others

is there a little screw or a hole on the focuser where you put your eyepeice in? there should be

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Hi.

The older 90's Tal 1's had a few quirks.

They had a focuser which has a 32mm inside diameter. The eyepieces were 'held' in place, simply by a push fit. No locking thumbscrew. edit: the eyepieces were a much lower profile than their later standard 1.25"/31.75mm.

The scope came with 2 eyepieces and a 3x barlow giving a nice range of magnifications.

So. First things first. The eyepieces you have, probably won't come to focus because they sit out more(compared to the stock originals), from the focuser. Do you feel that you need to rack the focuser further in than it can go? If so, then you'll need to push the primary mirror further up, to compensate. Quite a few of us have done so, here on SGL. It simply means replacing the two sets of setscrews and springs on the primary mirror cell. I think a member on here may have some left over from doing his Tal 1 ?

A quick and cheap way to fix any slop with eyepiece in the focuser is to wrap a piece of electrical pvc tape around the eyepiece barrel. One thickness worth. It works ! There is a possible fix for the focuser to add a lockscrew on it. In the meantime I think I put a thread up containing a pdf file for the stripdown and rebuild of Tal R&P focusers. It'll be somewhere on here. It's worthwhile doing, even to just get rid of the old grease which is probably full of debris.

There also may be some threads on SGL, regarding updating older Tal 1's. I'll have a look.

Tal 1's, no matter their age are fantastic scopes. Don't be put off by your older one. We'll help you out.

I'm sure they'll be a lot of folk stopping by and will be able to offer great advice.

Andy.

Edited by AndyH
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If you have a look at astro-baby's Tal 1 stripdown guide, you'll see a pic of an early focuser.....

TAL-1 Telescope OTA Strip Down Guide

Later ones look like this.....

7101897719_72e508fd53.jpg

I take it, yours is like the one on astro-baby's pic?

Andy.

ps: Both focusers are the same externally and with similar rack and pinion mechanisms. Only the interior focusing tube differs.

Edited by AndyH
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The older TAL 1 is a perisher for eyepieces. The older TAL eyepieces had their glass quite close to the bottom of the EP. Newer eyepeces almost never do being back up the nosepiece a bit more.

This is quite a curse, depending on the the EP it might be impossible to pull off. The amount of extra in focus needed for a Vixen NPL on mine was around 1" and as you will all be aware in focus is a killer.

Its aggraveted by the fact that its really hard to get another focuser that fits because of the location of the TAL 1s secondary mirror / spider screws which impinge on almost any other focuser.

i cut down a standard skywatcher focuser off of a broken 130 but unfortunately it sits too high. Thats why my TAL rebuold guide has stalled. Finding a decent focuser.

You can attempt to move the primary mirror further up the tube BUT you run into a problem that the stock screws are too short and when you out longer ones in the mirror becomes unstable as its balancing on the long and thin screws.

Its a taxing problem for sure. A have some ideas for redoing my own one which inlcude having the rear end of the tube remachined to take about 1.5" off it.

Part of the hazards of older TALs I am afraid and one of the reasons I always advise beginners to get something from a shop. Bargains on ebay can be royal pains and doubly so for the unwary.

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Hi there, I have the same scope and the same problem, dont despair!

You have the original 25 and 15mm ep's and 3 times barlow?

If so you should be able to use any new ep with the the barlow and they work fine.

I have the standard ep's plus a 12mm celestron lx so I get 32x, 54x, 96x, 162x and 200x (with 12mm celestron plus 3 times barlow) that gives a good enough range for me.

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I used to have a TAL 1 and it did have slightly larger eyepieces than the 1.25 ones.

You could try a barlow which you can pick up relatively cheeply which may allow you to bring the eyepieces to focus..

If it fails then you can just sell it on.

I would go this route first before cutting the OTA..

Also put a wanted add on astro buy and sell for old TAL eyepieces as somone might have some in there loft!

As others have said its a nice scope so worth having patience with it..

Mark

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Moving the mirror up on the mirror cell works, ONLY if the longer replacement springs are very strong. If they are, then the mirror holds as steady as a rock.

I've done this fix to both my Tal 1 and Tal M (80mm newt). I originally tested them by throwing the ota's from one sofa to the other, a few times. Held collimation perfectly then and years down the line, still do.

Here's the link to the thread with the focuser stripdown/rebuild. Worth doing, in my opinion.

http://stargazerslounge.com/discussions-scopes-whole-setups/143960-tal-r-p-focuser-rebuild.html

SGL member , 'yeti monster' had a clever fix for the old Tal 1 focuser. He put a ring on the top of the focuser drawtube which let him use a thumbscrew, to lock the eyepiece in place. There were details on the Tal User Group, but that's no more, so perhaps pm him regarding it?

I think SGL member 'heathenwoods', may have some replacement setscrews and springs available. If he doesn't see this thread, send him a pm?

If for whatever reason, my only scope ended up being my Tal 1, it wouldn't be a bad thing !! Cracking scope on a mount perfectly suited to it.

Cheers,

Andy.

Edited by AndyH
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Wow - Thank you all for such a response - This forum is great !

The picture that AndyH has posted is similar to my focuser but not the same . The inner part (that travels up and down) is made of bright metal - possibly aluminium. There is no locking screw or device to hold the eyepieces in place - the eyepiece just drops into the focuser. There is a small small split in the top of the focusser which forms something akin to a spring. I think the eyepiece is supposed to be pinched by this spring action, but it is all a bit loose - Thanks Andy the suggestion of using pvc electrical tape looks as though it will fix this.

The problem with the focusing appears to be that the eyepieces need to travel nearer to the telescope tube (not further away), and there is insufficient travel to make this happen.

I hadn't thought about cutting the end of the telescope tube off, - but a friend of mine is good with metal and I could probably get this done, although I think I would prefer to try some longer screws first before I do something to the telecope that is irreversible.

Andy - do you have any idea how long the screws would need to be. If anybody has got any spares or know where to look for them I would be really grateful.

Thank you all for this - this is my first telescope and also my first forum experience. You guys are superb !

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DON'T cut the tube !!

If you take the primary mirror cell out of the tube, you'll notice that the inside diameter of the tube has had about 1mm machined off, about an inch or so into the length of the tube, for a great fit of the mirror cell. If you were to cut an inch or so off the tube, the cell then wouldn't fit in the tube!!

Try private messaging 'heathenwoods'. I'm sure he mentioned that he had a set of the setscrews and springs left. If you get no joy, then I'll find my notes of the sizes and where to get them.

Cheers,

Andy.

ps: Did you click on the link to astro-baby's page with a pic of the old focuser? Is yours the same as that one?

Edited by AndyH
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There is a small small split in the top of the focusser which forms something akin to a spring. I think the eyepiece is supposed to be pinched by this spring action, but it is all a bit loose

Bang on sir! That's exactly how the old 32mm o/d eyepieces were held in place.

Thanks Andy the suggestion of using pvc electrical tape looks as though it will fix this.

:D Cheap n simple. You can worry about doing a more professional fix in time.

:)

Andy.

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Andy

I have clicked the link. Yes that looks like my focuser.

Thank you so much for your advice - I have just whipped the mirror cell of the end of the telescope and see what you mean about the inside of the tube being reamed out - I certainly won't be cutting the end of the tube off !

I will send heathenwoods a message and let you know how I get on. Thank you.

Lumpnuts

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Andy

Now this probably is a silly question. How do I send a personal message to heathenwoods ? I'm not familiar with this site and am not sure where I find this facility.

Thanks

Lumpnuts

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If you click on the community tab at the top of the page then click members list, have a search for the person.

Once found, look under the members avatar for the 'send message tab.'

Cheers,

Andy.

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Hello Lumpnuts, Unfortunately I can't help with your focuser question since my Tal1 is a 2003 model with the 1.25 in focuser. I have EPs from Tal and other makers and they all come to focus. I have heard of many folks moving the mirror to allow the older ones to work...Len

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Hi gurneyfan67. Thank you for getting in touch.

It is reassuring to know that there is an answer to my problem.

This is the first time I have used a forum site - I have been overwhelmed with the help that people have offered. Its been a really good experience. Thanks.

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Hi Len.

I remember reading that pdf, years back. I reckon it was in the back of my mind when thinking about modding my Tal M(which I did, long before my Tal 1).

I think the full length strong springs and full length locking setscrews mod, is the way to go, rather than this one. Much more stable, in my honest opinion.

Cheers,

Andy.

Edited by AndyH
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