Auroras could illuminate the skies in some northern U.S. states this weekend as charged particles from the sun collide with Earth, offering a chance to get great night-time photographs.
The U.S. National Oceanic and Atmospheric Administration's Space Weather Prediction Center (SWPC) issued an alert on Thursday, cautioning that two geomagnetic storms were likely to occur on Friday and Saturday.
A geomagnetic storm is a major disturbance to Earth's magnetic field, often triggered when the sun shoots out a cloud of charged particles at our planet. These clouds are known as coronal mass ejections, or CMEs.
Geomagnetic storms can have all sorts of effects and come in varying strengths. The one that is likely to occur on Friday is the lowest on the SWPC's scale, which goes from G1 to G5. Another, stronger G2-level storm is expected to occur on Saturday.
The potential impact of the storms—particularly the G2 one—are power grid fluctuations, increased drag for satellites in low Earth orbit, degradation of high frequency radio signals, and the occurrence of auroras at latitudes lower than usual. This means it might be possible to see the northern lights in states such as New York, Wisconsin and Washington, the SWPC said.
However, this will likely be dependent on having clear, dark skies at night in regions free of light pollution.
The auroras might not occur, but if they do they can make for dazzling views and colorful photographs if they're snapped in the right way. Luckily there are online resources to help budding night-time photographers get the most out of any auroras that occur.
The crucial element for aurora photography is having a camera with a manual mode that allows the user to edit capture options for longer exposure times, such as shutter speed, f-stop and ISO. Longer exposure times mean the camera is better able take in the light it's seeing, bringing out night-time details and color that a human observer might not notice. In addition, a tripod will be necessary for keeping images blur-free.
Photography website Dave Morrow Photography advises that minimum f-stop values ranging from f/2.8 to f/4 are good for aurora photography. F-stop values control the size of the camera's aperture and thus the amount of light that enters the lens.
Shutter speed controls how long the camera allows itself to be exposed to light before snapping the image. Longer shutter speeds mean brighter images, but also risk introducing blur. The Dave Morrow Photography site states shutter speeds of between 1 and 15 seconds are recommended for aurora photography.
The ISO value is the camera's sensitivity to light. According to space news site Space.com, a good ISO value for aurora photography is between 800 and 2500, with a lower value representing less sensitivity.
The key things to focus on are how bright and fast-moving the auroras are, so experimenting will be useful. Just remember to take the lens cap off.
