Moon and Aurora: friends or enemies?
Earth’s own natural satellite and the aurora borealis are the two major sources of light brightening up our long arctic winter nights. Do they affect each other? Do they compete?
When you have never seen the aurora in real life you simply cannot imagine the amount of light it can produce against a dark sky. However everyone has more or less experienced how much light the moon can shed to illuminate a starry landscape. The two sources of light are very hard to compare though. The moon is this tiny but very bright dot in the sky and the aurora is very spread out and varies highly in intensity.
New moon to first quarter
Picture taken at Storvatnet on Senja showing a 15% illuminated moon, the still visible milky way, deep-sky objects and a faint aurora
When there is no moon in the sky the aurora shines with the most contrasts. It tends to take on more yellowish and reddish colors. You can even see the faintest aurorae when the solar activity is not very high. As the moon is between 0 to 10% illuminated (thin crescent) it barely makes any difference. There might give a slight bluish hue to the sky. However when the crescent gets bigger things begin to change. At around 20-25% illuminated our natural satellite start washing off the faintest aurorae and deep-sky objects.
The aurora colors start shifting towards the blue. The greens get less yellow and more emerald and the red canopy tends to appear magenta. However at this stage a big auroral display still easily wins the light battle over the moon as it engulfs the whole sky. Towards first quarter (50%) the moon starts getting very bright. The faintest aurorae are now washed out and so is most of the milky way. The landscape starts being nicely illuminated.
Picture taken on South Senja showing a 40% illuminated moon. A modestly bright aurora is still visible and colorful. Notice the magenta on top…
First quarter to Full moon
During this phase the moon is very bright. As the moon nears full, it sheds so much light on Earth that it kills all the contrasts in the sky. The milky way is completely invisible. For the aurora it is a bit different. The faintest aurorae are certainly invisible by now. However the amount of light produced by the aurora during the expansion phase of a sub-storm can be significant. Not only that but when the aurora is very bright its colors are still visible with flashy greens, yellows and pinks! At full moon the aurora cannot outshine the aurora per se. For example if we refer to the shadows they cast on the ground, even a big aurora outburst cannot create a stronger shadow than that of the full moon. Nonetheless at that stage it’s almost as though they compete with each other. And the aurora is not far behind in spite of popular belief!
Full moon and aurora competing to outshine one another from the observatory.
In total actuality lots of aurora chasers call it quits when it’s around full moon. It’s all a question of taste but the moon can actually give spectacular results in terms of atmosphere, experience and photography. At the observatory our favorite auroras are honnestly the ones experienced under a full moon illuminating a landscape covered in snow. The aurora might be less contrasted in the sky but it still produces loads of naked-eye visible colors. The snow and clouds around participate in creating a true winter wonderland. It was by far the most appreciated moment for our guests this year (and for us as well!).
Example of a fainter aurora under the full moon. It is perhaps less visible but the winter wonderland experience is unforgettable!
This is what happened 15 minutes after the previous photo
In the two pictures above we really want to show you that despite what a lot of people think the moon should be the aurora’s ally and not its enemy. It sure washes it off but it does create absolutely stunning nightscapes. The shadows and colors complement the aurora quite nicely as you can see on that last picture taken from the observatory (our personal favorite this year!).
In conclusion if you were wondering if you should travel to see the aurora according to the moon calendar, it is completely up to you. It mainly depends on the general experience you want to have. Lots of people actually love the moon because they can see outside when there’s snow and it creates this picture-perfect wintery landscape. Some people want to see the aurora in its full glory on a moonless night, which is a totally different experience.