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Tal 100r Objective air gap

france79uk

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france79uk

france79uk

Posted
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Hi All, wonder if anybody can help on this one. Have just picked up a used Tal 100r that is in ok condition and at a guess about 8yrs old. The 3 x 120deg metal spacers that form the air gap on all the Tal 100`s I have seen are not present, does anyone know if some 100r`s were produced without spacers and this is normal? Also there are Newton rings round and central in the objective which suggest tight spacing I would think. If it does need spacers I have some thin ally foil 0.005". 0.14mm that I could use. Have trawled the net for articles on 100r /rs refurb but without luck. any help appreciated. Paul

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AndyH

AndyH

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Posted

I'm sure there's been a similar request on the Tal/NPZ forum. It rings a bell. I'll have a wee trawl. I don't think you'd go (far)wrong with the foil spacers using std kitchen foil?

I'll post back any definitive info.

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AndyH

AndyH

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Typical construction of lenses of all of our refractor, see below.

The first lens is flatter surface outward. Axial clearance A between the lens 0.3 mm (TAL-100). The lens is joined to the pipe diameter in the smooth and secured with three screws with heads vpotay. Threaded ring 4 (normal, not the split) simply insures the lens of a vypadyvaniya only lightly touching her. The air gap A is given by three spacers 5, affixed to the lens 2. The magnitude of this gap affects the spherical aberration. Coma is eliminated transverse displacement of the lens 1. Astigmatism? its reversal. Chromatism determined optical constants of glass and therefore unchangeable.

But in general I must say that resolved on the alignment of the lens should be only in extreme cases, when clearly visible image defects and it is suspected that the lens is subjected to disassembly. Usually the plant achieve the best possible image quality and damage can be very easy, but to improve it? unlikely!

Attached Image

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Sadly it's an old post and the image has been lost due to forum upgrades. I'd guess by reading the above (poorly)translated passage, the spacing should 0.3 mm???

I managed to get 0.3mm on my kitchen foil with multiple folds.

The only way to know for sure, I guess, would be to fire off an email to Yuri Elovenko at uran@npz.spektr.siberia.net

Andy.

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  • 4 weeks later...
ronin

ronin

Posted
Posted

I would also ask about the lens orientation.

The extract says:

The first lens is flatter surface outward.

This is unusual for the reduction of spherical aberation, in this orientation the front lens is introducing a high degree of SA that then has to be designed out.

Not saying that they did not manage to design it out but with what I guess is just an air spaced doublet it would be difficult and would not allow the designer to minimise other aberations as they would have to concentrate on the SA.

Sort of why introduce a problem to then put effort into removing it.

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