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Kowa TSN823m juddery focus knob (1 Viewer)

chris murphy

Used Register
Evening all

I have purchased a Kowa TSN823m with a 32x wide eyepiece from a well known online auction site.
It looks in reasonable condition but having just test-run it in the field I have issues with the focus knob, it is not smooth when making small adjustments and is a bit 'juddery', making fine focus difficult. Is this a common or known feature, or does it indicate that something is deteriorating in the focus mechanism?

I am quite surprised at the performance of the scope, I bought it to complement my 663 as I wanted a bigger objective for better low light performance, but doing a side-by-side in the gloom of dusk I was hardly able to notice much difference between the two. If anything, my 663 looked a little 'crisper' and had much smoother focusing.
The eyepiece is the fold-down rubber eyecup one, so I assume the coatings on my 30x wide on the 663 are probably improved.
I intended to purchase this scope and fit a Baader Hyperion mkiv eyepiece for a nice bright wide field zoom, but with the focus issue and the disappointing low-light performance I'm now not so sure. I'm thinking of maybe just sticking with my trusty 663.

Anyone have any thoughts or experience with the focus issue, and any possible solutions?
Thanks in advance.


Well-known member
Hi Chris, I had an 823 for a brief period that I picked up at a very reasonable price as the previous owner had done a repair to the focus system. As I recall the focus wheel attaches to the prism mount via a very small hook, and this kept snagging on mine which meant the focus didn't always work.
Not to alarm you, but when I bought it, it worked fine for a while, but the focus became increasingly "ratchet-y" with use before the mechanism finally broke.
I recall the scope was ok optically (mine was also a bit dull), but I didn't miss it when I replaced it with a used APO-77 (subsequently replaced by an ED82 which I find difficult to beat!).

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