Understanding

  Aurora 101  

     In one easy step (Aurora 101)
     or a few more detailed steps (Aurora 202)

  This web site is a compendium of information from several web sites listed at the end of this article.


Aurora 101

How:
In a nutshell, aurora occurs when charged particles from the sun hit the earth's atmosphere and cause the air to glow.

Where:
Aurora occurs 100-300 km above the earth in the aurora oval, a circle a few thousand kilometers in diameter around each of the earth's magnetic poles. Northern Canada, Alaska and the extreme north of Europe and Asia are the most common places to see aurora. Occasionally, the oval will expand and aurora can be seen further south in places like the United States and central Europe and Asia.

When:
Some aurora is in the oval all the time but it is usually too faint to see. The best time to look is within a couple of hours of midnight on clear, moonless nights, away from city lights. The globe below shows you how often you're likely to see aurora from various parts of North America. Sometimes aurora can be predicted. More on that in Aurora 202.

 

This has been a quick overview. If you want a more detailed explanation see ... Aurora 202


To photograph the aurora

You'll need:

If it's cold:

Aurora varies in brightness so there is no one exposure time that works for all cases. Try the suggestions listed below and bracket widely (that is, take several pictures with different exposure times. Try 1/4, 1/2, and 2 times what is suggested below). Set the focus to infinity.

Exposure Times (seconds):

Film Speed (ISO)

Aperture
Settings

50 100 200 400 800

1.4

50s

25s

15s

8s

4s

1.8

80s

40s

23s

12s

6s

2.0

110s

50s

30s

15s

8s

2.8

220s

110s

60s

30s

15s

3.5

--

--

90s

45s

23s

4.0

--

--

120s

60s

30s

Very bright aurora photographed with a Sony DSCW1 digital camera: 10 seconds at f/2.8, ISO 400.


More aurora images

On to Aurora 202


Links for some of the material in this article and for further reading:

http://www.birchwoodtours.com/aurora/52/default.aspx

http://www.gi.alaska.edu/asahi/color.htm

 


Send comments and suggestions to Chris Brown


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