Create your own realistic maps out of astronomical object images in 3060 minutes! Subtitles are provided.
Key times in the video:

1:35 Creating the initial height map.
3:59 Refining the height map and land sculpting
8:08 Putting in Erosion effects with WILBUR
13:05 Applying Land Bumps, Color Gradients, and Water.
16:17 Touching up lakes.

See my DeviantArt page for more examples and other maps, including the final result of this walkthrough in full resolution: http://ferocefv.deviantart.com/gallery/

An Excellent source of space photos: http://heritage.stsci.edu/gallery/gal...

Special thanks to Arsheesh for his own excellent tutorial; check it out below, along with the other tools you'll need to follow along here.

Tools:
GIMP: http://www.gimp.org/
WILBUR: http://www.fracterra.com/wilbur.html
Eriond Tutorial: http://www.cartographersguild.com/sho...
Nebula Image: http://vignette2.wikia.nocookie.net/p...
Or find your own image at: https://www.spacetelescope.org/images...