I was imaging last night, only managed an hour on the Cocoon Nebula. What caught my eye was the artifacts showing on the stars. The thing is this hasn't showed up before. Up to now my star images were circular. The only thing that I have done since my last imaging session is cleaned my objective lens (carefully...blower brush, lens tissue\fluid then a very gentle polish with a microfibre cloth). I'm very careful handling the scope, no knocks etc. If this is aperture vignetting how can this suddenly appear, and if it's pinched optics the same question as nothing has changed barring the lens clean. Here's an image to show the effect - the little notch at the eight o'clock position on the brighter stars (low rez but you can see it). Hope anyone can shed some light on it and hopefully a fix !