Star trails traced by a constant hand

Last weekend I visited the University of Canterbury’s Mt John Observatory. I had been granted time on one of the telescopes during the darkest nights of the month. The waning crescent moon was mostly absent from the sky, rising a couple of hours before dawn. Throughout the night I used a powerful digital camera attached to the telescope to take multiple long-exposure pictures of galaxies and nebulae.

With individual exposures lasting between five and 10 minutes, there is plenty of time to step outside the observatory control room. Without fail, that time is spent appreciating the inspirational beauty of the Mackenzie sky.

Under the jet-black celestial sphere, just for fun, I often set up one of my collection of film cameras. I use them to take long exposures that I develop in my darkroom upon returning home.

On this visit to Mt John, I was keen to try out a new addition to my collection; a panoramic camera that uses 120 film to record wide-angle images.

All of the analogue pictures I take record the motion of the stars during the exposure. Of course, it is not the stars that are moving, it is Earth.

The rotation of our planet during the hour-long exposures makes the stars appear to move in the sky. These long-exposure images also show what is going on around the observatory.

You can see light trails at ground level caused by the flashlights of passing astronomers. If you are lucky, you capture their ghostly silhouettes as they contemplate the heavens.

The first of this week’s accompanying photographs was taken as the moon rose last Saturday morning.

It is not only the stars that seem to move in the sky. The sun also rises and sets. It also changes its position over a year because of Earth’s orbital motion.

The second of this week’s photographs was taken from a pinhole camera that I left at the observatory in July 2021 and took down last weekend. It is a record of the sun’s motion over 195 days with New Zealand’s largest telescope in the foreground.

 - Ian Griffin