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Skywarden,
Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki
taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Quiet aurora arc - 12.10.2017 at 00.53 Espoo Observation number 67481

Visibility II / V

Janne Sievinen, Ursa (Helsinki)

The first northern lights of the season, for my part, were photographed in Solvalla, Espoo. The shooting started at around 11:17 pm, when the slightly more active period seemed to be coming to an end, and at 00:53, at the beginning of a more active session, the camera battery was running low. The balance 330 shots with 15-second exposures, a video of which is attached. For the first time, a battery-operated lens heater was also included, without which shooting would have stopped after just a few pictures, as the air cooled to +2 C and the relative humidity was exactly 100%. However, the fogs remained on the son of the valley and there were good unobstructed views to the north from the top of the ski hill.



More similar observations
Additional information
  • Aurora brightness
    • Dim auroras
  • 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.

  • Observed aurora forms
    • Veil info

      Veil
      Veil is the most bland and very common form of aurora. It usually covers its homogeneous dim glow over a wide area of the sky at once. Most often, the veil is seen in the calmer and quiet phase of the night after the aurora maximum as a background for other forms. The veil can also occur alone and in that case it will be quite difficult to reliably identify as an aurora, especially at a observation site which has a lot of light pollution.

      A similar glow of light can also be caused by airborne moisture, smoke, or a very thin layer of clouds that reflects the light that hits them. However, clouds can also be used to identify veil, especially if the middle or upper cloud appears dark against a lighter background, then it is very likely to be aurora veil if the brightness of the background sky is not due to the rising or falling Moon or Sun. When photographing, very long exposure times usually reveal the green colour of the veil auroras.

      Veil and rays. Photo by Esa Palmi.
       

      Red aurora veil. Photo by Marko Mikkilä.

       

      Veil. Photo by Milla Myllymaa.

       

      Aurora veil that changes color from green at the lower edge through purple to blue at the top. Photo by Jaakko Hatanpää.

       

      Dim green veil. Photo by Jarmo Leskinen.

       

      Radial aurora band surrounded by veil. Photo by Jussi Alanenpää.

    • 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.

Technical information

Exposure: 330 x 15s at 14mm f / 2.8 ISO800. Equipment: Canon EOS 650D & Samyang 14mm 1: 2.8 ED AS IF UMC, W&W Astro Dew Heater wrapped around the objective.

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