At first, I though it was a Photoshop too.
I did some research. It does look like a Sky under that tarp.
I also zoomed into some of the Photoshop points everyone pointed out and I do see some parts as suspect.
My speculation is that black “sky” is actually the Opel GT itself but just PhotoShopped to make it look better, like they do with other glossy car pics. Its like Stuff Magazine except the rear is that shinny.