TAL 100 RS - collimation on a refractor

[TonyD]

Andy,

Thanks so much.

This is all going in my "knowledge base" I am compiling so when I get the scope I have easy access to all this invalualbe information.

Tony

[Astro_Baby]

Tony....awwwww fanx but in truth its Andy H here who is rhe real maestro of TAL hardware.

I cant be bothered to create a picture by the way of my weird collimation view with a cheap cheshire but what I am seeing is a bright white dot at the centre of the lens and two doughnuts aroind te dot. One doughnut is at the 10 o clock position and the other at the 5 o clock position, they are exactly opposite each other and slightly overlapping. One doughnit is fainter than the other.

My bet is ai am seeing EITHER two doughnuts because each pne is reelected from a different part of the doublet lens OR the fainter one is an echo of the firts refelected back up the tube from the cheshire....that seems unlikley to me. To eliminate the doughnuts the focuser would need t be tilted at least 15' out of true and that seems very wrong. The only other thing I can imagine is that one lens of the doublet group is misplaced but I cant see how.

Now all of that would make me suspect somethings out f true EXCEPT I see exactly the same result no matter which diagonal I use, ie one thats been adjusted to be definitely out of true and one thats in perfect alignment.

What makes this very strange is that the scope performs perfectly. Perhaps. Should leave well alone but its got my curiosity spiked as to whay the cheshire is returning such an odd result.

Next weekend I will be able to experiment more and look into a few other things.

The TALmanula gives a list of double. Stars you should be able to split and advises if you can split them then theres not much wrong, typical Russian deep seated common sense there. Unfortunately the weather has been so atrocious for so long I'd be happy to see the moon let alone an exotocs deep sky double

A nice old one on a wooden tripod looks lovely by the way Tony andI am sure you wnt be disappointed.

[TonyD]

but in truth its Andy H here who is rhe real maestro of TAL hardware

Yes, Andy isn't the "Russian Informer" for nothing. Check the other thread he is helping me with

Tony

[AndyH]

Hehehe.

I'm no maestro, just a Tal-oholic. All the info I've picked up is really from loads of sites and other folk and it seems to have stuck. Okay, I've got 1 or 2 Tal scopes, so it helps enormously, when you've stripped down n rebuilt them, but I blame that on the weather. I guess I'm a Tal 'Rain Man'. Wish I was like that with other subjects when I was at school !!!!!!!

But, Astro_Baby, you are too modest. Your pages regarding Tal stuff and others are inspired. Take a bow curtsy !

I had NOTHING to do with the 'Russian Informer' thing either. Makes me giggle though. My father is convinced I'll be on the MI6 watch list because of my communicaes, in Russian, with the Southern Siberian Homebase. Mwahaha.

The internet was set up as a communication tool and to help spread info. Just doing my part.

A_B - I can't offer any assistance with your cheshire probs, especially as Santa must have had me on the naughty list(no cheshire for xmas). Hopefully moderator John might read this and help. He sounds like he's knowledgable in that regard. I would say that many of us can get overly obsessed(Johns words, but I agree). No matter how or what I use to collimate, nothing beats a good star test. Probably around 200x for the Tal 100? If the airy rings are nice n concentric and the patterns look the same inside and out of focus, that'd do for me? Which reminds me, I mentioned to Jules(nightfisher) that I'd try and see if an artificial star could be made out of a Maglite, kitchen foil and a pin. Refractors tend to be able to achieve close focusing(I've done so with my Burgess in the house) and the 100RS does have a very long focus tube. An indoor artificial star is a great thing to have.

Andy.

[AndyH]

Struggling to get a small enough pin hole. My hubble artificial star becomes a better buy, everytime a piece of tinfoil is crumpled and chucked at the wall

My 2 fracs work in the house, albeit with lengthy extensions for straight through work. But if you know your diagonal is a good un, that cuts the need for so many extensions.

I'm getting the most glorious in focus airy disc on both, which more often than naught, is next to impossible due to our rubbish seeing conditions.

For the price of a cheap plossl, this device gets a big thumbs up from me !

Andy

ps: I'll persevere with the MagLite/tinfoil for a while.