The Andromeda Galaxy, Mirach and Triangle Galaxy

This is the entire frame. I noticed it myself, but I don't know what causes it.

And yes, thank you for the note and the suggestions. I'll need to test it with other lenses of the same focal length, and then figure out if the issue might be with the Chinese adapter. :)

It seems to me that if the adapter were misaligned, it would cause a uniform blur relative to the center of the frame. But here it looks very strange. The top isn't as affected as the bottom. So I'd be more inclined to blame the lens... Possibly something with the lenses inside, maybe some are misaligned or something like that.
Although, generally, such lenses aren't the best choice for astrophotography :) They create swirly bokeh, and at the edges of the frame, you can really see how everything gets twisted :) That looks nice in portrait photography, but for astro—it's no good at all :(

For now, I'll make do with what I have.