Stars appear stretched in Siril stack result
Hello everyone!
As a total newbie to astrophotography, I attempted to take some photos of Cassiopea, in order to experiment and get a bit familiar with the entire process.
I have taken around 120 light frames and even though I'm not sure I got my lens focused correctly, they look relatively sharp. I also took bias, dark and flat frames.
My next steps were to organize the photos in folders (named biases, darks, flats, lights) and run the OSC_Preprocessing script in Sirl.
However, in the result .fit file the stars in a part of the image appear stretched, to the point they overlap with each other creating a blur.
In addition to that, there are also some red artifacts on the upper right corner of the result image.
I have uploaded some images here so you can inspect on your own: https://imgur.com/a/XQy5wu0.
One thing I should mention is that I use a custom lens hood (modeled and 3D-printed by yours truly), which I suspect might have caused some vignetting in my light and flat frames. Additionally, I believe the red artifacts might have been caused by the custom lens hood in combination with the red headlamp I was wearing.
The custom lens hasn't been an issue in normal (non-astro) photos so far, but I guess the issue just happened to become visible only under the current circumstances.
That said, do you think the blur could be caused by the vignetting on my light frames? And either way, do you see any way I can work around it (like cropping the frames) and try to get a decent result out of Siril's preprocessing?
The camera and lens I used are:
- Nikon D3400
- Tokina AT-X 11-16 PRO DX (with a custom lens hood), set to 11.5mm
- no mount
Also I used a shutter speed of 20s and ISO was set to 3200.