Basically just curves and USM, with a tiny bit of hue/sat. A broad selection was made using quick mask and gradient to select sky or land (switch between using select>inverse).
USM was used for both sharpening and local contrast enhancement. Basic steps:
- Global curves (set black point, white point, adjust white point for blue independently)
- Select sky (gradient)
- Curves
- Hue/sat (slight boost to reds)
- USM (local contrast)
- USM (sharpen detail)
- Select>inverse to select land
- Curves
- USM (local contrast)
- USM (sharpen detail)