Wednesday, 19 April 2017

Odd radius plate arcs in diamond dust display

The lamp in the photo is a couple of degrees below the horizon and there are 18, 20, 24 and 35° plate arcs. Plus a bit of a helic arc that in this kind of display could be of the odd radius type or at least contributed by it. This stage lasted only a few minutes after which lesser halos were visible for the rest of night. Under the outdoor light shining in the photo an upper 23° continued its presence longer. The display appeared on the night of 5/6 January 2017. Temperature was -27° C.

The photo below shows the location. The camera-lamp configuration is not the same as for the photo above, where the lamp and the camera were more level.

Friday, 14 April 2017

Recent displays from St Petersburg, Russia

In this post, I'm including the most interesting displays observed during the last month.

14th March 2017

On that day, halos appeared in the morning in separate cirrus clouds. Their arrival was not predicted by the meteogram. When I looked out from the window, I saw a bright CZA, but when I came down, it had disappeared. Nevertheless, I could see the weak supralateral arc. Half an hour later, I also saw a nice infralateral arc, when the cirrus cloud reached the horizon.

29th March 2017

In the evening bright parhelion was detected, and then a little while later also the wide circumzenithal arc. The halos were produced by the anvil of a convection cell.

1st April 2017

In the morning, at 10-00, the sky was clear. But in the south-west direction, low over the horizon a lot of cirrus clouds were visible. Their arrival was extended for an hour and a half. When a border of a front of cirrus clouds started to arrive, I noticed that it was weak and almost transparent. When these weak clouds reached the sun, at first I did not notice any halos. But soon, some markers of sub-visual odd radius display appeared.

It was broad and undefined halo in 22° area, with pretty obvious upper 23° plate arc in some moments. In the reflection of my sunglasses these things were visible a lot better. These weak odd radius halos were visible for around a half of hour, or even more while the area of weak cirrus crossed the sun.

Then, on the right-hand side pretty bright 22° halo started to appear. It was the arrival of main part of cirrus. In that area clouds were common and solid. After few minutes both bright tangent arcs appeared. Lower tangent arc was brighter than upper. I also noticed big infralateral arc on the right-hand side. It was pretty weak, but well coloured. I could see the arc better when I used peripheral vision.

This peak of the display was rather lengthy, and during its course I also watched both 120° parhelia, parhelic circle (it was easily seen within 22° ring), and the top part of 46° halo (likely it was the combination of supralateral arc and 46 halo. Although both were weak, together they became visually visible).
The peak was interrupted when middle-level cloud started to arrive. Then I saw a couple times only bright 22° halo

7th April 2017

The display looked quite ordinary, so I was glad I detected pyramidal halos such as upper 23° plate arc and 9° column arc.

9th April 2017

On that day, there was only a weak 22° halo. But the stack discovered also 18° halo/18° plate arc

10th April 2017

It was the weak display, which lasted most of the day. There was no suspicion that there may be pyramidal halos. But still I got upper 23° plate, 18° plate arc and 9° halo in the stacks.

Tuesday, 11 April 2017

Halo Phenomena in Olaus Magnus’s Historia de Gentibus Septentrionalibus (Part 3)

Halo phenomena in Historia de Gentibus Septentrionalibus, Bk. 1, Ch, 16. Image from

“And no wonder: since we are so constituted, that everyday things, even if they deserve our amazement, pass us by; on the other hand the slightest things if they spring up in an unfamiliar way, become a pleasant spectacle. (…) when anything varies from normality, everyone’s face is turned to the sky.” (Ch. 15.) No one who is interested in halos would say that Olaus Magnus, the 16th century Swedish theologian was not right when he wrote this. Even nowadays, most people rarely look up, and they take the sky for granted. If however, there is a comet, eclipse or halo phenomenon which becomes hyped by the media, people’s head immediately turn up for at least a day or two. But why not longer? I’m always surprised.

We have arrived at the final post of our three-part series introducing Olaus Magnus’s description of halos in Historia de Gentibus Septentrionalibus (part 1, part 2). This 16th century work dedicates several chapters to halo phenomena and illustrates the descriptions with fine woodcuts. According to Olaus, halos tend to appear mostly on spring mornings, especially when the surface of the earth is covered by deep snow and they usually don’t last more than one and a half or two hours. As he states in Chapter 15, this is due to the fact that clouds tend to change very quickly: they either thin or thicken too much for these phenomena to be observed.

This latter statement is indeed a realistic one, but scientific accuracy is not a characteristic feature of Olaus’s work. Historia de Gentibus Septentrionalibus was printed just around the advent of the scientific revolution, in 1555, when interest in natural phenomena was growing. Olaus is a Renaissance author, who lays much emphasis on collecting and recovering the scientific knowledge of ancient writers. However – although he tries to explain the formation of halos – he does not venture into looking further than the sources of the Antiquity and contemporary superstitions. This becomes evident when he continues his argumentation about clouds: (…) since they are caused by the reflection of the black clouds and the whiteness of the very thick snow which wholly covers the face of the earth, [halos] are chiefly seen in February and March, because of the distant, slanting position of the sun”

As for contemporary beliefs, in Chapter 15 he treats halos together with comets and talks about them as bad omen, signalling “change of existing order” and meaning “grievous prognostications”. He, however, does not elaborate on halos affecting social order; in these two chapters he mostly mentions them as signals of unfavourable weather. “The blacker clouds in the lower circle foretell that savager tempests are on their way” (Ch. 16).
Halo phenomena in Historia de Gentibus Septentrionalibus, Bk. 1, Ch, 15. Image from
From the strange description that Olaus gives, and also from the woodcuts, it becomes evident that personally he never witnessed the appearance of such phenomena. (…) one circle, spacious and entirely white forms in the clouds over the horizon, but with another on its inner edge, which is black from being more compressed in size. On their surface these very large circles have four lines, or round openings distinguished by their saffron colour; between these towards the south among white clouds that are filled with snow, appear two circles set opposite each other, one of which is black on its outer rim, and on the inner, white. The other, lower circle, in the centre of which the disk of the sun is seen (this is intersected by the upper circle, which has a different centre) is white on the outer rim and dark on the inner, though the nearer the sun it lies, the whiter it is. Moreover, opposite the sun, round about the centre of the very large circle which spreads, as I said, over the horizon, there appears a bow lying diagonally, with colours like those of a rainbow, amid thick clouds, reddish on the outside, purple or saffron-yellow in the middle, and green below.” (Ch. 15)

Olaus’s Historia was written several decades before the three famous historical displays that marked a milestone in halo-science. It was the Rome displays of 1629 and 1630 which aroused the interest of Descartes so much that he decided to turn to halos. His publication of Les Météores in 1637 meant the first step towards a modern explanation of halo formation. Mathematical and physical approach to halos only started with his work and (after the 1661 Danzig display) it was further elaborated by the Dutch Christiaan Huygens. When reading Olaus Magnus’s Historia, we should not forget that at the time of its publication, the real scientific revolution was yet to come.

By Ágnes Kiricsi

English translation by Peter Fisher and Humphrey Higgens from: Olaus Magnus, A Description of the Northern Peoples, 1555, Vol. 1. Ed.: Peter Foote, Hakluyt Society, 1996.

Sunday, 9 April 2017

Lunar display with Lowitz arcs and an unknown arc

On the night between February 10 and 11 a bright lunar halo display in diamond dust was observed in Tampere, Finland. Bright and well defined Lowitz arcs were the most prominent feature. In addition, an unknown arc can also be seen extending downwards from the parhelion. The display was witnessed by Jari Luomanen and Johanna Järventaus.

More images available at:

Friday, 7 April 2017

Close to melting point: a case of high temperature diamond dust

Melt waters draining into sewers and flies warming up on the building walls. You wouldn't expect diamond dust on an such early spring day, but that's just what happened on 6. April in the south-eastern Finnish city of Joensuu.

As I came out from Sokos department store where I went to buy herring (which they didn't have), I was surprised to see ice crystals glittering against the town hall building and ground, making a vague spread out subsun on front of me. For a second I thought of the possibility of tree twigs shedding off their snow (a couple of years ago a guy stacked subsun formed that way) but it did't feel right because for one thing there was no more snow on trees. So I looked up and saw in the sun direction myriads of crystals speeding past in the light wind. This was true diamond dust: the fog that had settled previous day at the darkfall over Joensuu was now clearing up and trying to turn into ice.

Next my eye caught parhelia. They were visible intermittently for 25 minutes until the fog evaporated away. I tried to see cza but could not spot it. Sun elevation during the observation rose from 29 to 30.5 degrees, which is near the end of cza visibility range at 32 degrees. If the crystals were optically below par, as seemed to be the case judging from the rather tame appearance of parhelia, that may explain the absence of cza at such an unoptimal sun elevation.

I don't carry thermometer, but at the official weather station some 1.5 km away temperature changed from -0.2 to -0.3° C (31.6 to 31.5° F) during the time parhelia were seen between 10:55 and 11:15. Joensuu is flat over large areas and I wouldn't expect much temperature differences between my location by the river and the weather station, particularly in fog situation where temperatures should be evened out. If anything, where I was it should have been warmer, because I could see that the station direction was fully enshrouded in fog whereas I was at a transitional area between total fog to the south and completely clear blue sky to the north and thus air must have been warmed up slightly by the sun. By 11:30 it had cleared all around and the temperature at the station was already +1.3 C, thus testifying on the warming effect of sun.

A vertical temperature profile would of course have been interesting as the mass of the crystals seemed to form a bit above the ground. Possibly it was a bit colder up above. On the other hand, the ceiling of the fog has been all the time in full sun shine, so it is hard to say. Maybe a someone versed in meteorology would have an insight on this.

An earlier halo observation near melting point is that by Jarmo Moilanen in Oulu on 3. November 2013. He saw parhelia, subsun and subparhelia at -0.4 to -0.6° C (31.3 to 30.9° F), but by the time Moilanen got camera ready the display had already faded and there was only subsun visible.

View towards south where it was full fog over the lake

Thursday, 6 April 2017

9° Halo

Before leaving for work I saw some decent cirrus clouds and looked up and saw 22d halo complete circumscribed halo and sharp 9d halo and taking the pics I enhanced them after coming home.

Wednesday, 5 April 2017

Some diamond dust odd radii in Rovaniemi

These photos were taken on the night of 9/10 February. In the image above we see odd radius stuff in the beam: circular halos and some bulges on them indicative of poorly plate oriented pyramids. The arc straight above the lamp on the broad 22° halo should be Parry / upper tangent arc rather than upper 20° plate arc. Visually I could not see the odd radii stuff but the appearance of the glitter made me think for its possibility.

One additional reason to suspect odd radii was the lunar display, which did not seem like your basic 22° halo stuff. The shot below was taken soon after I turned off the spotlight and it indeed has some not so clear odd radii, partly because of the artefacts. I photographed lunar also before the spotlight, and then the stuff was even poorer (this photo is not shown). So the spotlight in between gave the best display, which is of course what one expects

The enhanced version of this photo really brings out the artefacts. Br fouled it so completely that I am not showing it. Up until now I had had this nuisance entering the scene only in raw sun shine, but now it is has expanded its range to moon lit nights.

On the brighter side the artefacts became less disturbing when the milky background started clearing as shown by the photo below. Yet even then the br gives a rather ugly result.

Sunday, 2 April 2017

Subvisual odd radius halos in the UK

In the afternoon of 26 March, 2017, I was spending time outdoors with my family and wasn't too well equipped for serious observing. Of course, I had paid some attention to cirrostratus clouds drifting in the sky, but most of the time I struggled to see any significant halos. There were just occasional patches of 22° halo: or at least that's what I thought they were. But then the upper suncave Parry arc appeared so I had no choice but to start photographing immediately. After all, you don't get Parry every week, and in fact this was my first such encounter in 2017. During the next 20 minutes or so, I took a decent set of photos, but then gave up as it appeared that the display had become insignificant again.

My hope was to find a few more halos in the post-processing, and stacking did a good job indeed. The stack shown above is from the first 50 frames and covers a total of 196 seconds. On the left the unsharp mask is applied on individual frames before stacking. The version in the middle is a gradient-subtracted average stack, which is further processed by using the blue-minus-red subtraction technique on the right. In addition to the usual stuff and the Parry arc, we can identify upper and middle Lowitz arcs as well as a short piece of helic arc to the left from the circumzenith arc. But that's not all - there are also odd radius circular halos.

For comparison, the stack below is from the last set of 30 frames that I took more than 30 minutes after the last signs of the Parry arc had disappeared. This stack covers a total of 174 seconds. I didn't really expect to find anything special at this point, but took the photos anyway out of curiosity. Apparently the odd radius stuff is still in play. My feeling is that it had been there all the time, possibly long before I noticed the Parry for the first time and also long after I had got indoors to celebrate the Mother's day dinner.

What is shown below is an attempt to make the scene as clear as possible by combining photos from two different series into one stack. 100 frames are included, covering 13 minutes in time but missing about six minutes in the middle. My interpretation is that the relatively typical pattern of 9°, 18°, 24°, and 35° halos is complemented by the exotic 13° halo. But I'm not sure and it would be great to hear what readers might think of the case. Whether the 20° halo is missing altogether or masked behind the suspiciously wide 18° halo, I am not sure of that either.