Weird artifact NEOWISE last night

[Hals]

Imaged our transient friend last night and the coma shows a strange artifact. Obviously something with my scope but really annoying. I can process it out but it's got me stumped. Second pic is a crop of the autosave.tif after stacking, pre-processing.

Edited July 28, 2020 by Hals

[Hals]

Mods, I've posted this in the wrong place, could you please move to the Imaging - Widefield and Special Events & Comets section ! Thanks.

[Kyle Allen]

Did you use Kappa-Sigma Clipping algorithm when stacking? I find that I get the same result when stacking an image with a comet in it - presumably due to the comet moving relative to the background stars. If you set it to a different algorithm, you might find it keeps the core. Definitely nothing wrong with your scope though! 🙂

[Hals]

Cheers Kyle, I believe I did use K-S. I will restack and see what happens !

[Hals]

Restacked and it's definitely the K-S clipping that's caused it. I used Average this time and it's much better and wow, that is one fast moving comet. Even taking 30 x 4 second shots the movement it showed in this short time has really surprised me. Thanks again Kyle Allen for pointing me in the right direction. 👍