The attraction and distraction of refraction

Earth’s atmosphere is fantastic. It keeps us alive, provides oxygen to breathe and is a shield protecting earthlings from the worst the universe can throw at us.

However, there are many other reasons people living in our part of the world can admire the thin veil of gas that envelops our planet. The lack of pollution and a chance to see the sun, moon and planets in a pristine sky provide opportunities to experience sights that few people living in more urban and industrialised parts of the world can ever witness.

I was reminded of this on the evening of August 31. With absolutely perfect weather in prospect, I was determined to watch the much-heralded super full blue moon rise over the Southern Ocean. I headed out to Cape Saunders on Otago Peninsula, knowing I would have an unobstructed view.

As shadows lengthened with the descending sun, I set up my telescope and pointed it towards the predicted position of moonrise. Just after 6pm, I spotted a crimson arch peeping above the eastern oceanic horizon. The moon was rising! I started taking photographs and watched as the earth’s rotation slowly carried the moon higher in the sky. And for the next few minutes, I enjoyed one of the most spectacular and fascinating light shows I have ever experienced. The moon transformed from an arch to a mushroom, an oval, and a red-rising orb.

The effects I enjoyed as the moon rose were all caused by refraction. Earth’s atmosphere serves as a dynamic prism. This phenomenon occurs due to the varying density of gases in our atmosphere. When light from the moon travels through the lower layers of the atmosphere near the horizon, it encounters molecules, dust particles, and other atmospheric components. These elements scatter and bend the moon’s light, causing it to take a longer and winding path before reaching our eyes.

This bending effect, known as atmospheric refraction, makes the moon appear flattened or distorted when it is low in the sky. On Thursday, August 31, my eyes were treated to a masterclass of refraction by our planet’s precious atmosphere.