This shader is overall very good, but I think the black hole in the end looks very static, and an option to add a spinning effect would make it look a lot better.

Truth be told, the black hole isn't actually spinning but is actually using scrolling textures to make it "spin" but at a slow rate. This was done for optimization purposes and in my opinion the spinning doesn't really look as I have tried it when developing the black hole.

I know that the 'rings' of the black hole were moving, as I poked around with the shader code a bit a while ago, but I was more referring to the distortion of the skybox near the black hole. While messing around with the shader code, I tried to make this distortion spin, and while I got it to spin, the distortion also grows rapidly and eventually distorts the entire skybox, and because I'm not very knowledgeable in this area, I gave up. Here's a clip of that experiment to show what I mean.

During the development stages of the black hole it used to do this exact effect leaning on the idea that the sky will become more chaotic as time passes. However, the rings will eventually look unrecognizable as more time passes so I decided to with the current approach today.

I do get what you mean with the distortion affecting the sky box though. I'll see what I can do.

Thanks!