High-Cloud Tricker from Hungary

January 16 brought a whole-day high-cloud display to the greatest part of Hungary. The morning started with a spectacular sunpillar with bright upper-tangent arc, and the phenomenon became more and more complex during the day. Perhaps the most interesting feature of the display was caught by Ernő Berkó. He saw a Tricker-arc in Ludányhalászi, Hungary.


As he explained, he started reading emails from other Hungarian observers about the beautiful sunpillar of the morning, but in his region, there was thick fog with a night temperature of -17 °C. At 12:10 UT the fog disappeared, and he discovered the upper-tangent arc and the then symmetrical (about 60 degree-long) supralateral arc above it. Both were slightly coloured. While he was making preparations to take photos, the clouds thickened and covered the view. Later the conditions turned better again, the right side of the upper tangent arc strengthened, and he could take photos from 13:15 for 25 more minutes with the supra reaching lower and lower. He could see that it got brighter at the place where the parhelic circle crossed the upper tangent arc. It was only later that he realised the infralateral arc was also a bit visible and this caused the brightening. Ernő Berkó was trying to discover other halo forms but until 13:20 there were no other arcs, not even a 22 degree halo. It was only after this that the 22° halo started brightening here and there; the clouds were not uniform at all. A few minutes later he caught sight of the halos at the anthelic point. What he saw was mostly of the time a white oval brightening only, but the Tricker-arc also appeared, and sometimes a faint X-shape was also visible, suggesting Greenler arcs. To the naked eyes. the parhelic circle was invisible at this region of the sky. Later on the phenomenon weakened as the clouds thickened again. Ernő said he felt lucky that some days earlier he had shovelled a path in the snow to the back of his garden (where otherwise his telescope is), as this was the place where he could take images without many disturbing objects in view…and he caught the Tricker here, too.



It was Csaba Kozsa, who managed to take a picture of the infralateral arc. He was also reading messages in the buzzing Hungarian forum of halo observers, so in the early afternoon he rushed to his favourite observation point: Visegrád’s hill, Kis-Villám. This is the closest elevation to his home with a good view to South-Southwest, and the 270m hill made it possible to take a photo of the infra. He says that up till this day he had had very little knowledge about complex halo phenomena, but thanks to the several observations on Monday and the explanations of more experienced observers, he now knows where to look and what to pay more attention to.

A pure breed uppervex Hastings

In snow gun diamond dust displays Parry orientation is often strongly emphasized in relation to column orientation. There may be no signs of column orientation at all, except for perhaps a slight tanget arc brightening on top of 22° halo.

Such displays have made observers to ask themselves whether the uppervex Hastings arc – the Hastings arc component that is touching the uppervex Parry arc – could be sometimes be obseved in addition to the usual Wegener, or even without it. So far displays where light source elevation allows separation of uppervex Hastings and Wegener have not resulted in any candidates.

However, in spotlight displays where lamp is at or below the horizon, we have managed to photograph during the last and this winter a several of cases that are suggestive of an uppervex Hastings. And not even suggestive, but outright assertive.

The uppervex Hastings intensifies with lowering light source elevation, only complication is that it then starts to overlap with Wegener and identification must be done on the basis of other halos in the display. If Parry orientation halos are prominent and column orientation halos such as 46° lateral arcs, diffuse arcs and subhelic and Tricker arc are very weak or absent, then we might say that the “Hastgener” in the display is indeed Hastings arc.

As an example of a display that leaves little doubt of its Hastings nature, here is shown a one that Marko Mikkilä observed this year, on the 2nd January in Sievi. The lamp was resting on the ground on a rather level field and is according to Mikkilä about 3 degrees below the camera.

We see no evidence of column orientation – no 46° lateral arcs, no Tricker, no subhelic arc. Instead, in the image there is an overwhelming helic arc and Tape arcs, which both are solely Parry orientation born. Thus the faint “Hastgener” must be an uppervex Hastings arc, rather than Wegener.

Above is a attempt at simulating with HaloPoint. It supports the Parry scenario untarnished by columns, even though the details may not be quite right. Perhaps the most striking mismatch is with the subanthelic arc, which is bright in simulation but seems to be missing from the photo. However, there is a darker area which looks as if shaped by subanthelic arc. This seems to be a real effect, we have seen similar looking dark voids inside anthelic arcs before and in an upcoming post I will be showing a good example of such darkness associated with this halo. Perhaps the more intense parts of subanthelic arc are outside left outside of Mikkilä’s photo, although in that case it should have been possible to make a matching simulation. I actually did find an option which was better in that respect, but other parts got too wrong to take it seriously.

An earlier display in the same location by Mikkilä seems to also contain a pure uppervex Hastings.

A distinct Wegener but other reflection halos from column orientation lacking

By Marko Riikonen

Spotlight 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).

As for the posed question, I don’t have an answer. In simulations, using plate like column oriented crystals weakens subhelic and diffuse arcs in relation to Wegener, but they are still well visible, as shown by the simulation in the image below, which was done, I think, with h/d 0.3 plates.

Of the other stuff worth a mention in the image – which is a total of 27 min 20 sec exposure – is the sub-120° parhelion. It is quite common in spotlight displays, but to see it one typically has to run alonside the beam. This time it was clearly visible while standing still. There is also a blue spot. At 9 degree elevation it shares exactly the same location with 120° parhelion, which may be there too.

Another photo taken a bit later and at another location, shows a dark circular void at the zenith (or nadir, if you look from the point of view of halos), as shown below. A much more striking instance of this effect was captured by Jari Luomanen in 2013.

This night of halo hunt started on 8 November at 10 pm and lasted until 5 am. The development of the diamond dust quality was a slow and hopeless decline, which happens quite often when temperatures drop towards -15 °C. That is considered by halo hunters the worst temperature, giving crappy displays. Unfortunately the temperature notes were lost as my halo hunting diary got corrupted and shows now page after page ####s instead of letters. But I think it was between -11 and -14 °C through the night.

Diamond dust halos on the night of 12/13 January, part II

More photos from the 12/13 January night. The image above is a view opposite to the spotlight. Seen is blue circle, diffuse, Wegener and subhelic arcs. Below are two more images, the blue-minus-red image shows the “column 351/361”, which is the Kern arc equivalent of 46° supralateral arc. The lamp is about 5 degrees below the camera.

Marko Riikonen

Anthelic arcs in Finland

On August 28th anthelic arcs appeared in the northern part of Finland. My coffee break was suddenly halted as watching from the window I noticed several arcs. Once outside my eye was first caught by well developed parhelic circle. Then, looking up I noticed a colourful Wegener arc. Colours were red on the bottom and blue on the upper part. In the later stage of the display I noticed faint X at the anthelion indicative of the diffuse/Tricker arcs. I had no camera but my friend borrowed his camera equipped cellphone. Image quality is quite poor, but halos are still recognizable. Also Parry arc and 120 parhelia were present. Other halos were 22halo, parhelia, 22 upper tangent arc, parhelic circle, circumzenith arc, infralateral arc and supralateral arc. The display was noticed over large areas in Finland. More photos is here. Also see the photos by Arto Oksanen and Panu Lahtinen

By Marko Mikkila