Star trails are without doubt one of the most spectacular and surprisingly easy subjects to photograph. All you need to create the most sensational magic show is a clear moonless night, as little artificial light as possible and a little patience (a deck chair and a few beers or a flask of coffee will help too).
All you need in terms of equipment is a camera (of course), a wide-angle lens (a 24mm lens or wider will do perfectly), a sturdy tripod and a remote release cable to minimise any camera shake from touching the camera & tripod (or simply use the time-delay mechanism on your camera to activate the shutter).
The science & technology part is easy too – set your camera to manual mode, set the camera to shoot JPEG’s (yes, JPEG’s not RAW – they blend together easier), set the ISO to 800 and the aperture setting to f4 (depth of field is irrelevant when shooting far away subjects and opening the ISO & aperture will let more light in and keep the exposure times shorter) and set the time exposure to 30 seconds (if the image looks too dark then perhaps extend the exposure time up to 60 seconds and see how that looks).
The idea is to shoot a large collection of individual JPEG images and then blend these all together in Photoshop or some bespoke star trail blending software to create the star trail circle. The danger with digital cameras is that you can overheat and irrevocably damage the sensor and also just create excessive digital noise (from the heat) if you make singular long exposures so blending a collection of short exposures is really the only way to go.
The more exposures you can shoot and blend the more complete the star circle will become. The exposure below is a ‘quick star grab’ from about 23-minutes of repetitive 30-second exposures (shows how little time it takes to start getting the star trail to take shape); it is said that you need around 4 hours of exposures to get a complete-enough star circle but in this particular instance mosquito’s (and the risk from malaria in Mozambique) and the call for beer overruled any willpower I had to sit outside in the dark for that period of time.
Star trails are spectacular to shoot and easy to do so what are you waiting for, go on, get out there and give it a go…!