Dusk Photo Session

I think it was on Tuesday, that I woke up quite early in the morning and as I walked out to my living room, I saw the sky was reddish orange. Wow it was amazingly beautiful, so I took out my tripod and camera and started taking pictures of the horizon. Then  I tried to convert the RAW to JPEG format, I saw so much noise in the pictures. I was using ISO 100, Av mode and shooting timer.  What could I do wrong, then in the program, I had to lessen the sharpness to 0 (it was 3) and it actually softened up the rough edges where the bright light (the sun) shine.

The below picture is actually the result of it. Anyone has some ideas about this noise? Thanks!