The Starry Night, 164

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Time Out for Alaska
Fairbanks: Eine Kleine Nachtmusik


We set off for Fairbanks on Thursday midday with Jessica driving, Logan working via a wireless connection in the back seat of the pickup truck, and me with my head stuck out the passenger-side window like a ride-along dog. There'll be lots of mountain photos later. You don't bisect the Alaska Range on a clear, late winter day and not do lots of mountain photos. Lots. But having launched the Iditarod dog sled race and caught Denali on a crystal-clear morning, we were after the third leg of the Alaska trifecta: the northern lights, and that's what this page is all about.

Here's the day's forecast from the Geophysical Institute at the University of Alaska Fairbanks.


By the time we got to Fairbanks (350 miles), met Jess's family there, had dinner, and unpacked, it had been a long day. I opted to sleep on the couch in the living room rather than in a guest bedroom, the better to be able to check frequently for the aurora by stepping out through the garage onto the rear patio and walking out from under its roof to the back yard where 12-18 inches of snow seemed to be considering a career in glaciation. The high temperature earlier in the day was in the low 20's. The night was clear and "bracing" but fortunately very calm, starting in the single digits, approaching zero late. All in all, I didn't expect much, especially considering the forecasts for "quiet" or "low" geomagnetic activity. We didn't plan to get out of town for darker skies until the forecast was better and some rest was in hand. So I watched from a mature suburb in a loop of the Chena River, a few miles west of downtown Fairbanks.

I checked Ronn Murray's auroral monitor about 9:00, and it showed just the least glow in a broad swath across the northern sky. His camera was just a few miles away, so I pulled on my snow socks and my shoes and stepped outside. What I saw was pretty much as promised: a fan of soft light ran through the northern and northeastern sky.


9:10 PM. The bright star is the planet Jupiter; the haunches of Leo are just above and to the left of Jupiter; the faint stars of the Coma Cluster are embedded in the aurora. Not bad, but nothing special. I've seen the northern lights from Lake of the Woods, from ETSU's observatory in Tennessee, from varrious campsites in Wyoming and Montana, and from the cul de sac above our home in North Carolina. This show was less impressive than those displays, but Fairbanks being where it is, any time there was green light in the sky the situation was worth keeping an eye on. When I checked two hours later, the aurora had become brighter and better defined. I changed from a 24mm lens to the 14mm to bring in more of the sky.


11:02 PM. Things were beginning to shape up. The brightest curtain did indeed blow slowly in the wind, pleats and striations walking along it as I watched. Other, dimmer, curtains appeared and disappeared. Rather than stand outside, I retreated to a warm recliner, read, cat-napped, and kept Ronn's monitor site open in a window on my computer. Not long before 1:00 AM, a swirl appeared in Ronn's virtual sky. I went outside to see for myself how the lights were coming along.



1:00 AM. The lights covered the sky. They were neither particularly bright nor especially intricate, but bands of green lit up the sky in every direction. Those to the northeast, on the right side of this photo, moved much more nimbly than the rest of the aurora. Streaks and folds appeared and disappeared every few seconds. I waited outside, watching things get organized. By now, this was easily the best display I'd ever seen. Then, not quite fifteen minutes, later, things got good.

(Click for a clearer look.)

1:12 AM. Activity surged. One curtain after another wafted down from the north. I gather that the auroral circle had expanded, passing south of Fairbanks. Charged particles sleeted down from directly above me. I watched for a "corona" where the curtains are directly overhead and perspective makes them into a radial burst --close, but I didn't see a well-defined example. Multiple curtains appeared, each swaying in the solar breeze. Fine striations ran along each curtain, and showers of light began to propogate down them as well. When these pulses reached the bottom edge, the "hem" of the curtains seemed to sparkle. The light spread out and faded along the edge just in time for another fold and a fresh delivery of cascades to replenish it.

"Man, oh man," I thought, "If this is 'quiet,' then the sky must do this just about every clear night!"

I waded further out into the snow so I could aim the camera higher in the sky and kept shooting four second exposures while the lights played overhead.


(Click for bigness.)


1:14 AM. When these curtains faded --the coil on the left unwound, expanded, blew apart-- their replacements were much weaker. By then I'd been standing in the snow for almost half an hour and I was much too lightly dressed for zero. I headed inside and made the mistake of bringing the camera with me. The lens immediately fogged over, then frosted. If I had left the camera capped outside, I might have made more photos. I might have thought to crank the sensitivity and take some video. (I might have frozen to death.) As it is, my next nap turned into a good night's sleep. I read on Spaceweather that the show continued into dawn, cycling between active and quiescent episodes as I had seen it do, and that around 5:00 or 5:30, the display got really bright. Still, I had good stuff and needed the sleep.

Besides, this was a "quiet" night, right?

No. Turns out this was a "G2-class geomagnetic storm" triggered when a coronal mass ejection launched from the Sun a few day earlier unexpectedly sideswiped Earth. As it happens, I didn't see even another hint of the lights from Alaska.


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Except where noted, deep-sky photos are made with an SBIG ST2000XM CCD behind a 10-inch Astro-Tech Ritchey-Chretien carried on an Astro-Physics Mach1GTO. The CCD is equipped with Baader wide- and narrow-band filters. The internal guide chip of the CCD most often keeps the OTA pointed in the right direction (I'll let you know when an OAG or guidescope takes its place). Camera control and guiding are handled by Maxim DL 5.12. The stock focuser on the AT10RC has been augmented with Robofocus 3.0.9 using adapters turned on the lathe downstairs. A Canon 6D and a modded 50D find themselves mounted on an Orion 10" F4 Newtonian or carrying widefield glass on an iOptron Skytracker. Beginning in May 2013, PixInsight has taken over more and more of the heavy lifting -- alignment, stacking, gradient removal, noise-reduction, transfer function modification, color calibration, and deconvolution. Photoshop CS4 et seq and the Focus Magic plugin get their licks in, too.


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                   © 2016, David Cortner