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Ursa Astronomical Association
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00130 Helsinki

Ursa Astronomical Association

Quiet aurora arc - 14.10.2015 at 02.02 - 15.10.2015 at 00.30 Eurajoki Observation number 44199

Visibility II / V

SGO's magnetometer dropped about 500 nT, not when in the field to watch. Few clouds, about 15% of the sky, no clouds. Calm matte belt II, from west to northeast, up to a height of about 25 °.

Structure H, few rays mocked. Form A. Brightness 1.5. Color class c, green.

More similar observations
Additional information
  • Aurora brightness
    • Dim auroras
  • Observed aurora forms
    • Arc info

      ARC The arcs are wider than the bands and do not fold as strongly. The arcs are normally neither very bright nor active.

      The arc is probably the most common form of aurora. When aurora show is a calm arc in the low northern sky it often doesn’t evolve to anything more during night. In more active shows the arc is often the first form to appear and the last to disappear.

      The lower edge of the arc is usually sharp but the upper edge can gradually blend into the background sky. As activity increases rays and folds normally develop, and the arcs turn gradually into bands.

      An aurora arc runs across the picture. Vertical shapes are rays. Photo by Atacan Ergin.

      Aurora Arc. Photo by Mauri Korpi.

      Aurora Arc. Photo by Anna-Liisa Sarajärvi.

      Aurora Arc. Photo by Matti Asumalahti.

  • Colors with unaided eye and other features
    • Green auroras info

      Green, seen with the naked eye, is one the most common colors of the aurora. The green color is derived from atomic oxygen.

      Green auroras. Lea Rahtu-Korpela.

      Green auroras. Photo by Juha Ojanperä.

Technical information

With the Nikon D300s, ISO 3200 is already a little too noisy (a matter of taste), in the future 1600 max. Glasses: Nikkor AF-S DX 18-200, shooting settings 18mm f3.5-6.3 Sigma 10-20 EX DC HMS 4-5.6 shooting settings 10mm f4-6.3

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