Long focal lengths magnify everything in the scene, including any atmospheric effects. Wind, humidity, thermal currents, etc. can distort extreme telephoto targets. When you look at a bright star at night on the horizon, and it twinkles, similar atmospheric effects are involved.
As already mentioned, f/14 reduces sharpness a bit. f/8 is a good default setting for many lenses when you want sharpness and some depth of field.
Here's a similar scene of mine. Notice how the flagpole or antenna on the left side is wavy, and there are notches in the sun's edge.