On some more aspects of a display observed in Rovaniemi on the night of 9/10 November, 2016

In the previous post of this display I discussed two photos taken towards the end of the hunt, just before twilight. Now it is time to look at the photos taken earlier, from midnight onwards at another location. Please mouse over or click the photos to remove the milky veil that the systems adds as default to them.

Of the several stacks that were photographed, I made simulations of two that are shown below. Unlike the morning photos, now only one stricly oriented Parry population was needed to the explain the display’s halos from c-axis horizontally oriented crystals. So here we have a pure case of uppervex Hastings and nothing reminescent of Wegener.


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Thin plates in rotating Parry orientation as an explanation for the display on the night of 8/9 November, 2016, in Rovaniemi

8-9nov-taulukko-valmisIn an earlier post I told simulation attempts were not succesful for this display. Well, I really did not put that much effort into it. Now I have given it a fresh look and managed to get some succees.

The problem was the subhelic arc and anthelic arcs that could not be get rid of. In new simulations made with HaloPoint the subhelic arc issue is pretty much resolved and the anthelic arcs also play it low key.

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On some aspects of a display observed in Rovaniemi on the night of 9/10 November, 2016

This was a good no-hassle night of diamond dust hunt. The swarm was stationary and I didn’t have to pack up every 20 minutes to follow its whims. During the 6 hours of observing it was necessary to move only once. Also, both two locations were quite good concerning the light pollution. Especially the second place, where I wrapped it up in the morning ours, had a really dark segment which I used to light up the anthelic region.

As for the halos, the start of the night at around midnight was not so inspiring. As I arrived to the snow deposit area near the river, a sneak peek in beam revealed a run-of-the-mill plate display and I though it will just get worse because the temperatures were in the bad range, around -15 C. So I decided I might as well give some minutes for the half-moon display that had a smudge of Moilanen arc. In photographs it was transformed into a nice V-shape.

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A distinct Wegener but other reflection halos from column orientation lacking

58408_e6b1bf173a772112c7ee827c1b4a106fSpotlight displays are great in that almost every time you photograph them, you realize you understand halos less and less. This time the puzzle is: Why Wegener in the image above is so strong in comparison to other reflection halos? No subhelic arc is visible and neither there seems to be diffuse arc I think the spikes at the subanthelic point are lamp artefacts. Of course I can’t not say that for sure, but around the subanthelic point even weak stuff shows up easily to the eye, so had there been diffuse arcs, I should have noticed it. If we accept this, then, in addition to the Wegener, the only suggestion of column reflection halos is what looks like a short patch of Tricker arc cutting across the sub-Kern arc (see the simulation below for comparison).

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A possible new halo above Moilanen arc

average3A simple diamond dust display that I photographed on the 6th of this month in Rovaniemi, shows above the Moilanen arc another, weaker V-shape. As I uploaded the photo on Taivaanvahti, I was not conscious of the effect, it caught the sharp eye of Panu Lahtinen and Reima Eresmaa who commented on it. Then some photo processing made it stand out more clearly. The version above was worked by Nicolas Lefaudeux. It is a stack of 13 images taken during 125 seconds.

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A plate spotlight display on 5th November 2016

average-valmis6Showcasing the last winter’s spotlight displays is still under way, but fresh produce is already coming in. Here is the new crop that I harvested on the evening of 5th November in Rovaniemi. In the image above the lamp is around -6 degrees below the horizon and both parhelic and subparhelic circle are visible. Slight intensity enhancements in them on the side of the sky opposite to the lamp are suggestive of Liljequist parhelia. Included are also Sub-Kern and sub-120° parhelion. I did not spot sub-Kern this time, but the latter was quite discernible when running alongside the beam. As usual, it was a pale pillar of light in which no individual crystals were detectable – very different from the intense subparhelic circle patch towards the subanthelic point, which is always made of pure glitter.

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Diamond dust halos in spotlight beam in the evening of December 2, 2015

45921_3bfac9da40b093f7ff4ab1552ac073a8Here are shown the rest of the photos from the night that yielded the second capture of the anomalous Wegener/Hastings. From the golf course parking lot, where we took those photos, we walked into the golf course, and were able to place the lamp even lower down.

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Another occurrence of anomalous Hastings/Wegener


On the left anomalous Wegstings, on the right normal

In an earlier post we showed a photo of a weird downward curving patch of Wegener/Hastings. Here is another case that occurred 9 days later on December 2, 2015. This time we also got a nice comparison to normal “Wegstings” by superposing photos taken from the same camera position.

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