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 re-visited 13° halo observation from 2013, and some thoughts about the responsible crystal faces

Circular halos of 12°-13° in radius are named “exotic” because they do not fit in the (nowadays) traditional sequence of well-documented halo radii from pyramidal ice crystals (9°, 18°, 20°, 22°, 23°, 24°, 35°, 46°). The first known photographs of such a halo were obtained at the South Pole, December 11th-12th, 1998, by Walter Tape, Jarmo Moilanen and Robert Greenler. Up to now, there are only few more (Michael Theusner, Bremerhaven, October 28th, 2012; Nicolas Lefaudeux, Paris, May 04th, 2014).

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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

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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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Spotlight display with strong Moilanen arc (and a crystal sample)

45797_19c840d56e4e22e5729ed89c87cfe8dfAfter having been hunting diamond dust halos since darkfall, at 1 am we withdrew along with disappearing crystals back to aparment to sleep. But this did not mean calling it quits. The forecast was for the conditions getting better, so every one hour each of us woke up in their turn to check the situation.

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