Here are the results for the artifical elements exercise
Original shot 1

Edited shot 1 - fog and rain
To create this shot from the original I went through a few steps.
-In RAW, lowered the saturation of the image overall, as well as lowering the saturation of certain colours.
- Still in RAW, added in an exposure gradient to the left hand side to even out the exposure across the frame
- I introduced a few cloud photos from my archive to give the overcast/rainy look to the sky
- The fog and rain effects were painted in using my tablet, the fog was done with the normal round feathered brush, the rain was done with the "Water Colour Loaded Wet Flat Tip" brush (this brush gives the streaky lines you can see)
- From here it was simply a balancing act to bring the elements together using opacity adjustments

Original shot 2

Edited shot 2 - stars, day/night conversion
To achieve this effect I went through the following steps.
- In RAW, the overall exposure was lowered, and the saturation and luminance of the blues was heavily reduced.
- Contrast was increased slightly.
- On a new layer, the clouds in the sky were cloned out, new clouds were introduced.
- The starfield was created using the noise filter, copied, expanded and masked off to give different size stars.
- The moon (yes its too big intentionally) is a photo.
- The highlights on the windmill were painted in.
- Using adjustment layers, i selectively reduced some colour from the sky as it still appeared a bit too bluish.