Northern Lights tonight: Could your phone see them when you can’t?
Yes. The Northern Lights tonight could be so faint that your eyes barely notice them while your phone camera captures unmistakable shades of green, pink or red.
And with minor geomagnetic storm conditions possible Wednesday, September 16, across the northern United States, this is one night when taking a picture of an apparently boring sky might be worth it.
Seriously. Your assignment tonight is to photograph something you may not even be able to see.
Where could you see the Northern Lights tonight?
The best opportunity is across the northern tier of the United States, where even a relatively modest geomagnetic storm can sometimes put aurora low on the northern horizon.
At roughly G1, or minor geomagnetic storm levels, places including northern Washington, Idaho, Montana, North Dakota, Minnesota, Wisconsin, Michigan and northern New England have the better odds.
If activity briefly strengthens toward G2 levels, the potential viewing area could creep farther south into portions of Oregon, Wyoming, Nebraska, Iowa, Illinois, Indiana, Ohio, Pennsylvania and New York.
But there's an important catch.
Seeing aurora from Illinois isn't necessarily going to look anything like those spectacular photographs from Alaska.
Farther south, you may see nothing more than a faint grayish glow or wispy streak very low on the northern horizon.
Or you may think you're seeing absolutely nothing.
That's when things get interesting.
Why can your phone see the Northern Lights when you can’t?
Your eyes are incredible instruments, but they're not particularly good at seeing color in extremely dim light.
As darkness increases, your vision relies increasingly on cells called rods. They're fantastic at detecting faint light, but lousy at distinguishing color.
That's why a dark backyard doesn't look like a dimmer version of daytime. Eventually, much of the world simply starts looking gray.
Your phone gets to cheat.
Night mode can gather light over several seconds and use computational photography to combine that information into a brighter image. Faint red and green auroral light that doesn't register strongly enough for your eyes can accumulate until suddenly it's visible in your photograph.
Think of it like putting a bucket outside during a drizzle.
Your eyes are trying to determine how much rain is falling right now.
Your camera leaves the bucket outside for several seconds and then says, "Look how much I collected."
Same sky. More collected light.
And suddenly that boring gray smudge has turned green.
How do you photograph the Northern Lights tonight?
You don't need a professional camera. Start with the phone already in your pocket.
Find the darkest location you reasonably can with a clear view toward the northern horizon. Get away from bright streetlights, give your eyes a little time to adjust and look north.
Then turn on your phone's night mode, hold it as still as possible, and take several pictures. Propping the phone against something solid or using a small tripod can help because movement during a longer exposure can blur the image.
Most importantly, take the picture even if you don't see anything.
Check the photograph before deciding the aurora isn't there.
Cloud cover and light pollution can ruin the show, and aurora forecasts can change quickly. This also isn't a forecast for giant green curtains stretching across the entire country. The farther south you are, the more likely any aurora would be faint and confined to the northern horizon.
But that's precisely what makes your phone such a fun little aurora detector.
What determines how far south the Northern Lights can travel?
One number you'll hear frequently is Kp, a scale used to describe global geomagnetic activity.
Generally, higher Kp values mean aurora can become visible farther from the polar regions. Current expectations favor relatively modest activity, not the kind of major geomagnetic storm required to reliably send spectacular auroras deep into the central or southern United States.
But Kp isn't the entire story.
The magnetic orientation of the solar wind matters too, particularly something scientists call Bz. When it points southward for long enough, Earth's magnetic field can couple more efficiently with the solar wind and allow more energy into our magnetic environment.
That's why aurora forecasting can be maddeningly exciting.
The forecast tells us where to look.
Sometimes the sky decides the rest.
Tonight, take the picture anyway
We're accustomed to thinking that a photograph records what we see.
Tonight could give you a wonderful reminder that sometimes a camera can reveal something that was there all along.
So charge your phone. Find some darkness. Look north.
And even if you see nothing but stars and a dark horizon...
Take the picture anyway.
There may be considerably more happening above you than your eyes realize.
And once you've photographed an invisible aurora, you'll probably never look at an empty nighttime sky quite the same way again.
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