I am having an issue that I am hoping for help here. I take astro pictures using: Nikon D850 with a Sigma 14mm F1.8 Dg ART lens on a tripod. I usually take a 6-10 images of the the night sky and denoise with a stack in starry landscape stacker (SLS). Every once is a while after stacking in SLS I end up with a photo with grainy ridges and rings. Any idea what could be causing this? The exposure here is ISO 6400 for 13 seconds at F1.8.
This could be, as already pointed out, effects triggered by the initial processing of the images.
The web site has instructions for how they should be pre-processed before loaded into SLS:
In summary, they are:
- reduce the contrast
- turn off sharpening and noise reduction
- apply lens chromatic aberration corrections - but turn off all other lens corrections
- Set custom white balance