The strange case of the missing degrees

Taken just after sunset over the sea. Helpfully backlit by the red clouds are two headlands jutting into the sea, with a small gap between them. Google maps shows the one on the left to be a northern tip of Sicily, and the one on the right to be a southern tip of Sardinia. The map also shows there to be several degrees of clearance between them as seen from Gioiosa Marea in Sicily. But there's less than a degree between them in the photo!

So where did the missing degrees go?

[The uncropped photo was taken with a 500mm lens on an APS-C 1.5ish crop sensor with a horizontal field of view of 3 degrees.]