Aperture vignetting ?

[Hals]

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 !

Edited July 24, 2020 by Hals

[jambouk]

It looks like it is linked with subtle diffraction spikes, but in an asymmetrical fashion. 

Are you 100% sure it wasn’t there before the cleaning?

I don’t know how to fix it, other than to make sure that you’ve not left an obvious big smudge of something on part of the optics or displaced something, or seated the camera at an angle to the focal plane. 

I wouldn't have noticed it had you not said. If you don’t like it and the scope is new, I’d talk to the retailer.

On the whole, optics are usually best left a bit dusty. An air puffer alone does good; cleaning them otherwise often creates many more issues than it resolves. I also wouldn’t use a micro fibre cloth as I think this could still scratch the optics.

I hope you find a cure.