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Unusual for me to be asking for help BUT I have a few questions on my TAL 100 and not knowing beans about refractor maintenence I'd really appreciate some advice.

My questions relate to the pics below;

Question 1

I have noticed, quite by accident, that the large locking ring on the front of the scope (one of the cut outs of this ring are shown below labelled 'A') seems quite loose. I can easily push it witha fingernail. Question - how tight should this be ? I dont want to put undue pressure on the lens but neither do I want a lovely bit of glass to fall out in a dark field.

Question 2

I want to remove the front lens cell as theres some grot on the back of the lens. I assume to remove the cell I would remove the screws at the rear of the cell (one of these is labelled 'D' below). I would assume mark the cell and tube position so it goes back in the same place. Am I right ?

Question 3

I assume the other screws are for collimating the lens (one of three is labelled 'B' in the pic below). I have no intention of messing with collimation but how do you tell if a refractor is in collimation. I assume if stars show as small white dots and expand to large white blobs that are circular when defocused all is well.

Question 4

What are the small cut outs in the lens cell labelled 'C' for ?

Question 5

So long as I am removing the lens cell is there any value in flocking between the cell and the first baffle and, perhaps, flocking between the last baffle and the focuser assembly ?

post-14805-133877446669_thumb.jpg

Edited by Astro_Baby
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That A ring will be a securing lens ring and should be nipped up (not tight). the screws D will be to release the lens cell. I have in the past taken a doublet apart.. and I mean full apart to clean each lens. Not a major issue, but don't do it unless you need to.

Rob

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Rob - thanks for that. Would you say its worth flocking at each end of the tube ? Also how tough are fracs to collimate. I have heard really difficult by some, easy by others.

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Re collimation, I think they vary enormously depending on the lens retention system. I once did a TeleVue and there the front element (doublet) had three 'adjusting' screws but a call to TV indicated that they were there to lock the element once it had been adjusted by hand. The idea was not to use them as you would the screws on a finder, for example.

For a star test on this job I just illuminated, with a good cycle headlamp, a ballbearing stuck to black card. Great artifical star. I needed a long dark space and a friend lent me his condom warehouse for the morning. I daresay other warehouses would do nearly as well...

Olly

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Hello AB.

I have a Tal 100R, but haven't taken it apart as I've not had the need to.

Re. collimation....you are correct. It's the same as for any other scope, just make sure your defocussed stars ar nice and round.

Cheers

Rob

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Hi Astro_Baby,

Thought I'd throw my tuppence in as well :

1) Yeah as has already been said The locking ring shouldn't be slack

but tight enough that it wouldn't easily move.

2) Yeah to do it the screws marked D are the ones to use and your

thinking re marking the position is fine but I don't think strickly

necessary.

3) Yeah as Ollypenrice said its pretty much done in the same way.

4) Not sure, they seem to be filled with a slightly spongey

filler, maybe they were used when the cell was put together

to hold the lens or something. Shouldn't have to touch them I would think.

5) Well I flocked my Tal 100R in the 1st, 2nd and 4th baffle. I

found it very useful for cutting down the stray light passing the

baffles. I would think doing the 1st and 4th would be adequite.

Kathleen

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1/ The locking ring should be finger tight, no more.

2/ And to reiterate the other replies, yes the screws marked 'd' do indeed hold the lens cell on the tube. If it were me I'd mark the cell and tube and put it back that way.

3-4/ As for the holes with the filler stuff in, tal regularly do this to screws that are locking in collimation on lenses.

5/ I'd paint flat black or flock anything and everything. When the tube's apart you may as well go for it !

Cheers,

Andy.

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Thank you guys and gals - it is as I thought but I like to be sure before I start messing with optics whenever possible. I do trailblaze as well but I prfer not to on the whole.

Looks like a flocking session coming on. I was mostly nervous that I undo something and the lens pair fall apart and take about 10 million years to get back into alignment.

It all looks simple enough so I'll kick off and have a fiddle about at the weekend.

Kathleen - the 100R has (I am told) leaky baffles. The 100RS baffles are supossedly better. I have taken the back end off and there is some leakage but my bet is flocking between the front lens and baffle 1 should fix that.

Thank you everyone for your input which is very gratefully received.

Mel

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  • 1 month later...

How are you getting on with the 100r ? ive recently had mine to bits , baffles, focuser, etc .

I used a similar trick of just flocking around the edge of the baffles to stop the light passing the bad fit of each baffle, worked a treat !

I'd be interested to hear how yours is going.

Andy.

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The pair of "nicks" marked "A" are for a special assembly tool (equivalent to a very wide screwdriver!! - two tabs on a bar that drop into those nicks) used to tighten the ring. You dont need the tool but could make one by finding a piece of steel flat bar that is as thick as the nicks are wide. Cut to length so it just reaches across both nicks and use like the aforementioned wide screwdriver.

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I use a pair of wooden tongs to open those things - or VERY CAREFULLY two jewellers screwdrivers.

I havent messed with the TAL yet I have so much other stuff on that its been shelved for a bit. Its not affecting its performance so I thought I;d just leave it alone for now.

Performance on it by the way is phenomenal. I hate to admit it as a reflector fan but I am seriously thinking of dumping all of my scopes and going for a larger long focal length refractor. Maybe a TAL 125 or something bigger still. A nice 6" would be cool but If I do this I'd want super quality.

Edited by Astro_Baby
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