Here is the picture before and after its processing in DxO Optics.
The accentuation is clear and enhance greatly the impression of sharpness.
In the upper right corner, the gain in sharpness is impressive: numerous stars appear were some faint stars were inconspicuous. This is due to the combined effect of the Sharpness and Vignetting DxO modules.

Canon 350D + Sigma 10-20 at 10 mm open at 4 on a tripod. 30 s at 800 ASA.