Star trails are a must do, during any astrophotography session. They are perhaps some of the easiest shots to obtain. Simply point your camera towards Polaris (the north star), set your ISO as low as you can go (usually ISO-100) and open your shutter for as long as you can – the longer the better.
I took this shot with the 5D Mark III + Tokina 16-28mm f/2.8 @16mm, f/2.8, ISO-100 and a 30 minute exposure. It’s fascinating to see and experience. I topped my stargazing excursion with this shot. If you notice any off-color specs, those are hot pixels. As a result of the ultra long exposure, even at low ISO, the sensor will heat up and introduce this type of noise.
The image was not edited. Processing was done with Canon DPP and some color contrast enhancing in GIMP.