Kowa TSN-501 - my first scope, defect? (1 Viewer)

[misikuru]

Hello, I'm a casual birder and I received today the Kowa TSN-501, my first scope. While testing it at home, I realised that it shows a circle patch in the middle of the image. I see it regardless of the magnification and it's distracting. It becomes darker on a bright background and also, with a higher magnification, the contrast between the whole image and the spot becomes stronger. Although I wiped both lenses and my glasses, it's still there. When I move my eye, then it also moves. Does anybody know what it might be? Is it a defect? Does your TSN-50X also have it?

I'm not sure if my description is clear, so I'll attach an image. As I couldn't capture it with my phone, I've done a quick Photoshop to show you what I see. (I exaggerated the shade of the circle a bit, and the edge of it isn't sharp on the real scope.)

 

[misikuru]

I also realised that the body is not precisely built.

It looks perfect from this side,


but it's uneven here.


Probably it's acceptable since it costs only 250 euros, but as I have no experience with scopes, I can't decide if I should return it. I appreciate any input!

 

[Hermann]

Return it. That scope is not ok IMO.

Hermann

 

[dwatsonbirder]

I agree with @Hermann - something isn't right there, it looks as though it has taken a bump in transit and the internal prism is displaced. Return it for another same - the one I had and tested was well build (and tightly sealed), and did not show the optical aberration you describe.

 

[michalb]

I own the same scope, had a look through it right now - no "dark patch" issues at all. The body looks tightly sealed as well, no issues as shown in your pics. Most probably you received a faulty one, as others point, better to return it and get another one of the same type - I can only say good things about this model, you can't beat its portability, I carry it on my bike almost all the time

 

[Peter.home]

I can actually see a lighter ring around the edge of mine, never would have noticed before. But it is about the same width as the yellow CA ring around the edge of the view.
About 1% of the view from the edge is affected, and I suspect It is only in extreme conditions. It's certainly not like your issue which looks like 50% affected

 

[misikuru]

@Hermann @dwatsonbirder @michalb @Peter.home Thank you for your comments, they were all helpful. I really appreciate that some of you took the time to check your scope. I've decided to return it and get a replacement.