Call it a gale of subatomic proportions. Once again, a gaping hole in the sun’s corona has unleashed a wind of electrons and protons bundled with magnetic energy toward the Earth. The blast touched off a minor geomagnetic storm earlier this morning with spillover expected tonight. After a lull, storming is expected to resume tomorrow morning (Sept. 28) and continue straight into the night. We can expect the best of it — a moderate or G2 storm — Wednesday evening, Sept. 28 from nightfall through 1 a.m. Thursday morning (Central Daylight time). Here’s the official forecast.
Basically, the next three nights look ripe for displays of northern lights. As long as the weather’s clear, conditions are ideal for viewing with no moon to brighten the sky. Get your cameras ready! You’ll need a tripod to use as a steady mount and a camera that can take time exposure photos up to 30 seconds long. Since autofocus cameras struggle to focus on stars, set both the lens and camera in manual mode. Then, either pre-focus on a distant cloud earlier in the day and leave the lens set at that position or use the live view option button on the camera back to directly focus on a bright star using the back viewing screen.
Set the camera’s light sensitivity to ISO 800 or 1600, the lens to its widest setting (something like f/2.8, 3.5 or 4) and compose the scene. Wide angle lenses are best for covering the the large auroral forms. You can either select the length of the exposure on your camera’s display or using a dial. If you have a “B” setting, that stands for “bulb”. In “B”, you can hold the shutter button down for as long or as little as you like. As soon as you let up, the exposure is over. Better, purchase a cable release-type device on Amazon or eBay or your local camera store that will do the pressing for you without having to worry about shaking the camera.
I like to start exposing at f/2.8 with an ISO of 1600 and exposure around 15 seconds then decrease or increase the length depending on what I see on the replay. At that ISO I rarely go longer than 25 seconds. If the image looks too dim, increase the exposure. If too bright, cut it back. Since electrons are cheap, shoot lots of photos to get something you like!