The Aurora: Nighttime Observing Hours

The chart above shows how daylight varies through the year in Fairbanks, Alaska. There are four regions in the chart:

1. The central region represents daytime, when the sun is above the horizon. The boundary line to this region is the sunrise/sunset curve.
2. The twilight region. The sun is below the horizon but the sky is still too bright to see stars or aurora.
3. Marginal viewing region, when the sun is between 6 and 18 degrees below the horizon. The sky is dark enough to see bright stars and aurora.
4. Excellent viewing region, when the sun is more than 18 degrees below the horizon. Faint stars and subtle aurora features can be seen.

From the chart, the prime aurora-viewing season runs from September to early April. May, June, and July are the "midnight sun" months when aurora and stars are not visible. Most of April and August are marginal viewing months, because the sky does not get truly dark at night, but bright stars and aurora may be seen.

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Modified 11 August 1999 by ddr