Keeping an eye on the night sky

Half of one rotation of Earth, captured in 500 images last week.IMAGE: IAN GRIFFIN
Half of one rotation of Earth, captured in 500 images last week.IMAGE: IAN GRIFFIN
Astronomy compulsives sometimes get a tad upset when our day jobs mean we can’t stay up quite as late as we want, writes Ian Griffin.

Ian Griffin. Photo: Otago Museum
Ian Griffin. Photo: Otago Museum
Very often, an early morning meeting requires having to pack away our kit with the sky still clear overhead. It is enormously disappointing to wake up after an early night discovering that I’ve missed an aurora, meteor, or some other celestial happening.

To avoid such frustrations, I have recently re-purposed a washing line poles. It is now the base for a new all-sky camera system.

A tiny black-and-white camera with a fish-eye lens now perches atop the pole. It is protected from the elements by a Perspex dome, which is equipped with a little heater, which prevents frost and dew formation during long winter nights. Intelligent software enables the system to continually monitor the sky brightness. Once it is dark enough to see stars, it starts taking pictures every 90 seconds.

At night’s end, as the sky brightens, the camera turns off and converts the images into a movie to enjoy as I eat my cornflakes. This camera system has changed my life for the better.

Since installing it a few weeks back, I have been able to enjoy the constantly changing sky above my Otago peninsula home every morning. As you might expect, the movies show lots of clouds and even the occasional raindrop. However, when the sky is clear, I’ve spotted dozens of meteors, satellites, and even a new exploding star (which was, unfortunately, discovered by someone else!)

One of the most fascinating things about my new morning ritual is watching the apparent motion of the stars through the course of the night. Of course, it is not the stars that are moving, it is the Earth. Just for fun, I have combined 500 images taken by the camera during one completely clear night last week to create this week’s image. The star trails show precisely half of one rotation of Earth.


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