Star light trails in a photo

Gemini South Star Trails - Elke Schulz (Nasa)
Gemini South Star Trails – Elke Schulz (Nasa)

Digital Photography School, in the middle of many a good photo tutorial, is publishing explanations on how to make a photo with nice circular star trails like on the image on the right.

4 Steps To Creating Star Trails Photos Using Stacking Software

In short:

  1. Choose the right location (a good sky view, with proper decor)
  2. Choose a low ISO setting (for long exposures)
  3. Shoot multiple images
  4. Stack the images together using a special software (Photoshop should allow it too)

Not too difficult. This must be quite feasible.

Do you have an example to show?