I’ve been meaning to shoot star trails for years but never really had a reason to explore the envelope - until now.

I have been commissioned to do some interesting shots later in the year that would really benefit from incorporating star trails but I knew next to nothing about the execution! In the shot below the gaps in the trails are simply explained - the timer stopped after 300 images and I fell asleep for an hour. I woke up and pressed the start button on the Nikon MC-36 Remote Cord but the camera batteries died after another hour and 100 odd additional exposures.

So how did I do this and what have I learned?

First the basics. In the northern hemisphere the centre of rotation is the North Star, just out of view in the top right of the image. The nearer that is to the centre of the image the more of a full circle you will achieve. Naturally the camera must be locked on a tripod and be dead solid. Then the rest is about staying awake, having a full charge in both the camera and the intervalometer and having spare battery packs ready for the camera if required. It is important to make sure that the moon, if there is one visible, will not pass through the shooting area as it is far too bright to capture successfully with these exposure times.

Typical settings on my Nikon D3S are ISO 200, Manual program set to Bulb at f/5.6, eyepiece shutter closed after framing, autofocus off, Vibration Reduction (VR) switched off, image review set to Off (this was where my excessive battery drain came from I think), Noise Reduction switched Off and shooting RAW files. It is also important to allow the camera to naturally cool down as the night temperature drops (to avoid condensation on the lens), rather than take it out of a warm house or car and expect it to work perfectly.

In this sequence each frame was exposed for 30 seconds, with a five second interval between each frame. The longer the interval between frames, the more of a gap between each element of the trails (like Morse code).

The single track railway, used by the local quarry, shows the same train travelling in both directions with a couple of hours elapsed between each journey. In the sky, just visible above the power lines as a series of dots, are the navigation lights of a pair of RAF C-130 Hercules flying right to left on a low flying night task.

I then imported all the images into Bridge and did my master adjustments in Camera RAW, applying that correction to all the files in bulk. That was the easy bit. I then sort of assumed that either file merging in Photoshop CC (or Lightroom CC) would achieve what I wanted, but even on my top-of-the-range 27” Retina iMac with 32Gb of RAM it just stuttered and popped and five hours later froze. I tried this three times and it seemed impossible. Not to be thwarted I then hunted around on the internet and found a free app called StarStaX that promised to do the job.

I next exported all the 400 files from Lightroom as high resolution, 50Mb least compression JPEGs and imported them into StarStaX which then took a mere 137 seconds at its default settings to render the result you see here.

To date this is my first attempt, but I'm looking forward to emulating some of the really great examples that can be found on the internet.

20160818

Star Trails - A First Stab At The Concept