2007. december 3., hétfő

More results from the latest display in Rovaniemi

Here is some more material from the diamond dust in Rovaniemi three nights ago. After the heaviest Parry-crystal bombarding was over, Moilanen arc appeared, as shown in the photo on the left. Moon gives the beauty spot.

I have crystal photos from this stage, but as usual, they give no clue to Moilanen arc. In the earlier Parry-stage there was no indication of Moilanen arc whatsoever, but I did not manage to get the crystals. This bugs, because comparing the samples might have pushed us forward in solving the mystery.

The upper left image shows parhelia from streetlamp - the stripes that are parallel to the electric lines. Then there are also arcs extending slightly obliquely downwards. While visually parhelia curved towards me, these other arcs curved away and around me. As far as I understand from looking at divergent light simulations by Lars Gislen et. al, this effect is a 120° parhelion. In the photo only the brightest part of 120° parhelia is seen, visually the crystal glitter extented much further. Also a full parhelic circle was seen visually.

The lower left photo shows what was seen around the half moon at its best. For long time there was hardly no moon halo, although in the beam of the halogen torch a great display was present. Some indication of Lowitz arcs is present in the moon photo. The crystal sample may be representative of this stage, but I am not sure.

5 megjegyzés:

  1. This post is fascinating as always. What made me think now is the top right-hand photo. Trying to imagine what divergent-light halos look like in reality (and why they are like that) requires some talent in 3-dimensional visualization. Having read now the Gislén et. al. articles (many thanks, Marko!), I started wondering if anybody has heard of any earlier documentation of the 120° parhelia produced by divergent-light. In the article "Observations and Simulations", there is a half-sentence saying that it "had probably never been seen" - at least as far as 2003 (p. 4278). I wouldn't be surprised to hear that this was the very first photo of what truly seems to be 120° parhelia based on the simulations.

  2. Ágnes, yes this might be first the first observation of 120 parhelion in divergent light.

    Michael, That is pretty much what is happening every time, even though I have seen some displays already. Just have to try to calm down and remember to take also those crystal samples. This time things were hampered by Nikon D70 corrupting memory cards one after another. It seems to have something to do with cold battery. After I made sure there was always warm battery in the camera, broblem disappeared. Many photos were copputed, but I got most of the recovered.

  3. Simply WoW...
    Will going to 6 day ski vacation to Kuusamo in the beginning of the February..I hope that the extra weight of the JohnLite will be worth the trouble.
    btw...I see you are using 8mm circular fisheye on cropped sensor...I have great news to you - Sigma has announced a 4.5mm fisheye for the APS-C cameras available in January, so we can enjoy full fisheye captures without going on expensive full frame.

  4. Yes, we are aware of the Sigma fisheye. Gotta think about it.

    Hoping diamond dusts during the Kuusamo trip. The diffuse arcs three weeks ago were photograhed with same lamp as yours (JML2940).

    Hopefully they will be running the machines in February in Kuusamo. I heard here is soon enough snow and then the machines are not used anymore during the rest of the winter - unless great losses happen due to warm weather. Now the weater is turning above freezing, so possibly that gives me an extra week or so.

  5. Marko If can you may want to get a hand warmer or a foot warmer and use that to keep the camera warm. That may sound strange but it beats no hear at all or a small propane heater.