Thanks for your comments Alfi! Yes, the sky is noisy, but it's intentional! I like the noisy sky simulating the "film" grain. I can easily make the sky silky smooth without a single trace of noise. But then it would be only half as interesting. When I return home, I will post the same photo without noise, to show you the difference. What's really bad is the burned sky. Unfortunately, it was not underexposed enough and RAW helped me to recover only a small part of burned sky
I actually don't care much about the sky in either version, both fine, even if they indeed are different. However, I like the grass field much better in the noise free picture and the hills in noisy picture. When you reduced the noise, did you also sharpen it a bit?