Ella reports on observing the stars from the South Pole

Dr Ella Derbyshire at the South Pole, image courtesy United States Antarctic Program

Alan Plummer: This winter Ella Derbyshire is at Amundsen-Scott South Pole Station where she is the station’s physician. The station is right under the South Celestial Pole at an elevation of 2,835 meters. On this trip – not her first – Ella had the thought to take binoculars with her for some stargazing. More to the point, Ella expressed an interest in doing some useful astronomy. As variable stars are the subject of active research and many are within the range of small binoculars I had the pleasure of sending of a set of charts and a choice of targets. Ella has since joined the VSS and the AAVSO and writes this report on what it’s like to observe where the Sun never sets. Over to Ella:

The bottom of the world is an interesting and challenging location for a novice variable star observer. Because the winter scientific research at the South Pole requires dark skies, we make conscious efforts to avoid light pollution. There are just enough thoughtfully-placed red lights outside to guide people from building to building as they walk through the dark. All our winter vehicles also shine only red lights. Once we arrive at astronomical darkness, our only two significant sources of light pollution are the moon, which rises monthly and then remains above the horizon for a fortnight, and auroras, which can be surprisingly bright and are far less predictable than the moon.

The map of the South Pole night sky is the map of the South Celestial Hemisphere. With the South Celestial Pole directly above us, and the Celestial Equator as our horizon, the star patterns are always in the same orientation, and so they are easy to learn. Stars do not rise or set here, they simple circle around us, inching a little bit westward with each passing day. With this simple arrangement, once I find a star in the sky, finding it again, assuming that it remains bright enough to find again, is easy.

I can choose any hour of the day for observations. Because target stars are always above the horizon, and the sky is as dark at noon as it is at midnight, the time of day that I choose to observe is not especially important. I just locate my guide stars, and then start star hopping.

Observing variable stars from the South Pole requires a bit of preparation. The coldest weather brings the clearest skies. Whenever it warms up, there is a persistent wind blowing, picking up the snow and tossing it in front of the stars. By the time that the temperature reaches -40ºC, the wind, which can reach 40 knots on warm days, is creeping up coat sleeves and under facemasks, threatening any inadequately covered skin with frostbite. Fortunately, staying outside to watch stars is pointless at such times because in polar wind storms, even Sirius and the moon are hidden. During cold, calm weather, with the temperature from -60 to -70ºC, dressed in a full set of extreme cold weather gear, I can stand still for almost an hour at a time, gazing up at the sky. If I get dark-adjusted before I venture out into the cold, I can make the most of these observing sessions.

In addition to chilling the observer, the cold affects whatever tools we bring outside. I record my results in pencil because ink freezes. Camera batteries die quickly, making astrophotography a real challenge. Camera lenses, eyeglasses and binoculars frost over with any misplaced breath, and must be warmed and dried to be useful again. It helps to be efficient at locating the target stars and comparison stars and at recording the results. After a while, even eyelashes frost up and will eventually stick together, providing an unambiguous clue that it is time to return inside.

Dr Derbyshire’s report was forwarded by Alan Plummer, prolific and expert variable star observer and a member of the Sydney City Skywatchers