“Randomized Moilanen half circle halo“ observed again in Ore Mountain Range diamond dust hotspot

On the evening of November 27th, 2015, a group of German halo observers including myself drove on top of Mt. Klínovec to witness a diamond dust halo display both created by the moon and artificial light sources. In a car headlight beam, I detected the upper half of what seemed to be a circular halo of radius 12°-13° by stacking video frames. Because we could simultaneously observe a (traditional) Moilanen arc at the moon, and experienced a considerable wind strength, I suspected that the orientations of the Moilanen crystals got randomized at eye level due to near-ground turbulences.

More than 3 years later, on December 15th, 2018, several halo enthusiasts were attracted independently by favorable conditions and met by chance on the summit of Mt. Fichtelberg, about 4 km north of Mt. Klínovec. After nightfall, multiple halo species created by car headlights became visible, such as the 22° circular halo, 22° parhelia, upper and lower 22° tangent arcs, 46° circular halo, parhelic circle and traces of the Moilanen arc. About 19:30 CET, Andreas Möller recorded a video of the glittering 22° ring and Moilanen spots. A maximum stack of the individual frames revealed that again not the familiar upward bent V-shape was present here, but a downward-curved segment of (likely) a circle:

photographed and processed by Andreas Möller

In effect, this confirms the earlier observation, though it still is a matter of definition if this phenomenon should be regarded as an individual halo species. So far, visual observations have only given the impression of independent glints, with the circular shape being only accessible through more or less elaborate post-processing of video footage.

Identifying light sources responsible for “floating” pillars

Recently, artificial light pillars were reported from Kuopio, Finland, which machted a city map projected into the sky. Artificial light halos are much less common in the German lowlands, especially in mild stages of the winter.

The more exciting it is, when nonetheless pillars from streetlights appear under such conditions. Of course they do not reach to the bottom then for the lack of crystals near the ground. This happened to me when cycling from a neighbouring village (Meuro) to my home (Hörlitz) in the Lower Lusatia region, on December 06th, 2018, a little after midnight (at air temperatures around -2 °C…-1 °C). My way led through a recultivated open coal mine (at roughly 51.53° N, 13.94° E), and I stopped twice to take photos of pillar segments that were floating in the sky at elevations of about 10°…25° in eastern directions. Their brightness was not great, as they were visible only in the dark outside villages and it took exposure times of about 30 s (at f/3.5 – f/4 and ISO 1600 on a Pentax K-5 camera) for decent photographs. The intensity also fluctuated over typically 30 s, depending on the changing number of properly oriented crystals at the right spot.

(00:33 CET, position A, f = 20 mm)

(00:49 CET, position B, f = 40 mm)

Of course, a very interesting question is where the responsible light sources were located. Under the assumption that the reflecting faces of the ice crystals are perfectly horizontally oriented, the light pillar is confined to a single azimuth coinciding with the the one of the source at the horizon, though the source itself may be rather far off and not visible. Luckily, some stars could be identified in the pictures from both observing positions (A and B), so the azimuths of the pillars can be determined. The brightest white pillar (1) higher in the sky and the brigthest yellow pillar (2) from the lower fence-like structure were chosen for further analysis:

(00:33, position A)

(00:44, position B)

When plotting the azimuthal directions from the two observation locations, intersections at 18.3 km (pillar 1) and 26.5 km (pillar 2) distance are obtained. These fit with the southern edge of the still active Welzow coal mine, and the Schwarze Pumpe power plant.

As the crystal positions, projected to the ground, are located halfway between the observer and the light source (see sketch below), they can be drawn on the map as well. The gray area above the lakes “Sedlitzer See” and “Partwitzer See” marks these locations as deduced from the pillar observations, though of course no actual boundaries of this area can be determined from this simple two-point study.

With the bottom distance d to the light sources known, it is straightforward to calculate the height H of the crystals above ground from the elevation angle h by simple trigonometry. The white pillar 1 in the image taken at 00:44 from spot B extended about 17.6° – 24.1° in elevation, and the yellow pillar 2 about 13.2° – 17.0°. It follows that the crystals were located at heights between 3.0 km and 4.1 km.

It should be added that earlier that night (Dec 5th, 20-21 CET), similar pillars were observed by Sören Petersen at Hohwacht, Schleswig-Holstein, at the Baltic sea. The distance to my location amounts to almost 400 km. Maybe the weather conditions favored the existence of a bigger ice crystal field at that time, as the rarity of such pillar observations in Germany renders a purely random coincidence unlikely.

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 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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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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