Interval Shooting at Night
There are numerous ways to do photography at night, for the majority of my night photography I’ve simply done single long exposure shots. So all the light would be captured on film or on the sensor in a single shot. If you are using a high ISO and wide shutter, you end up with a shorter exposure and get little to no movement from stars. If you use a lower ISO and smaller aperture, you’ll have a longer exposure and star trails as the camera stays open.
Using interval shooting, taking many short photos over a long period of time, you can get the best of both worlds.
For the following shots, I took 147 photos over a 45 minute window. The exposures themselves happened to be 15 seconds each, this depends on exposure for your scene, the key is the quantity of photos over the time window, a longer overall elapsed time will give you the most movement.
Afterwards, I can process these photos a couple of different ways.
First, using ffmpeg I can combine into a time-lapse video. I used the following command to create a video at 12-frames per second with 147 photos it works out to be a 12 second video.
ffmpeg -r 12 -pattern_type glob -i '*.JPG' -c:v libx264 -pix_fmt yuv420p -f mp4 output.mp4
Secondly, I processed the photos using ImageMagick and combined all 147 photos into a single shot, giving some quite nice star trails. I used the following command to combine the photos.
convert *.JPG -evaluate-sequence max combined.jpg