Things never go quite to plan do they...

So, tonight I received - for my efforts - a strange wispy artefact on my M1 image, this thing appears on all the 40 or so frames that I took... Any ideas?

I made a slightly better attempt at NGC2246, however it was so damn cold tonight that I had to abandon things before I got a really decent dataset, so I only had a couple of dark frames and no bias or flats. I guess that as ever - there's always next time! :)

https://en.wikipedia.org/wiki/Rosette_Nebula