If I install Optifine, and Kuda Shaders, I get a very strange issue where the sky lighting seems to follow my mouse cursor. The sky also has a weird mirror bowl like band to it.

This works fine if I do a custom profile on 1.12.1, with Forge, Optifine, and Kuda shaders.

Try enabling the "WeakRenders" option in the Astral Sorcery config.

We don't really support shaders but if the problem still happens in ATM3 4.0+ with/without the suggested config change let me know and I will look more into it.