Scintillation, also known as twinkling, refers to the change in brightness and color of stars through the atmosphere. If you have ever looked in the night sky and noticed twinkling stars, that was a result of turbulent atmosphere, small changes in the wind speed, temperature, and pressure. These small changes produce small changes in the refractive index of the air, which causes different wavelengths and intensity of light to enter our eyes - in the same way as light changes directions when it enters a swimming pool.
This image showcases that effect and it was created my moving the camera around during a long exposure of a particular celestial object. Notice the differences in line width and color between the stars and planets.
Location: Coyote Ridge, Fort Collins, CO
Camera: Canon XSi (modifed)
Lens: Canon 200mm f/2.8L + Canon 2x EF Telextender
Shot: Composite of Single Shots
10x1 second f/5.6 ISO 1600
Processing: Photoshop, Topaz