Artifacts on sky when Directional Light with Atmospheric Sun Light enabled

I was just trying to replicate the time of day example in template maps.

  1. I keep getting these artifacts like stuff on the sky around the sun as shown in the image. (circled in red)
  2. Also there is a set of straight lines on the sky as I have shown with blue color.

Is it because my sky sphere has a larger radius?

How do I fix these?

Currently, I am using a sphere with 10000 units or radius.
Before when I was using a smaller sphere, these artifacts were not visible