It has a bit of a painted quality to it. I just grabbed the first image I could find that would even remotely work. Over sharpened and the sky is a little too coloured, but it was done more so I could do it and get the knowledge in my head.
In fact I didn’t even use a panorama, just a dodgy single image. First one I came across where I thought the edges could be made to match.
Method taken from Photojojo’s article How to create your own planets using your panormamas (from way back in 2006).
And inspired by Bob Kueppers.
I’ll post some more when I take a few new panoramas.