Weak odd radius display with possible column arcs

This display occurred on 22th February 2017 in Izborsk (Pskov region, Russia). In the morning it was sunny and the first cirrus started to arrive around 13-00. In that moment, I saw a faint 22° halo, but it was visible because the cloud layer was smooth. Also it seemed to me that I saw a 9° halo through the viewfinder of my camera. The stacks showed pyramidal halos such as 9°, 24° and 35° halo.

The 24° halo looks pretty curious, because B-R processing shows the pause in 24° ring in area of upper tangent arc. It reminds me of 24° column arcs from crystals with big tilts. 9° halo also looks curious, brighter on the sides than on the top, what looks like 9° column arcs.

What do you think of that? 

Some photos of a Rovaniemi spotlight display

This was seen on 24 January 2017 in Rovaniemi. The image above is a total of 24 minutes exposure (48 frames). It shows all four kaleidoscopic arcs, which is not really that uncommon combo in the beam reality. Just before the diamond dust disappeared I took also a rare positive elevation lamp shot as shown below left. It's got 5 minutes total exposure. Below right is one of the first sets of the evening with 3 minutes exposure. The br reveals the insides of 46° and 22° halos are somewhat reddish.

It was quite cold, I think temperature was somewhere around -28° C towards the end of hunt. Unfortunately my halo hunt diary is no more because the folder called "halo" recently disappeared from the computer desktop without leaving a trace. It seems the universe don't want those notes to exist. Already earlier this season it got corrupted, all letters turned into #s. But I have a safety copy which has last winter's notes. At least for the time being.

Thanks to Panu Lahtinen, who stacked the image above when my Halostack had some mysterious glitch.

Artefacts from Hell

At the end of Marko Riikonen’s recent post, we hear a profound crie de couer about artefacts which plague some camera makes and models. For those of you who are blessed with top of the range, state of the art equipment, you might be wondering what all the fuss is about. Can artefacts which plague some cameras really be that bad? The short answer is a resounding yes, they can be horrendous. Moreover, for the type of work serious halo observers are engaged upon, these cameras are virtually useless. Marko mentions that for him the problems are exacerbated when trying to photograph during daylight but ease somewhat at night when recording spotlight displays. From personal experience with my own particular model, I can say that it is equally bad day or night. Here is an example of how bad it can get even at night. The image is of a simple circumscribed lunar halo with a faint 9° odd radius.

The halo is almost obliterated by the artefacts. This is one reason why I very rarely post anything these days because the images are just so embarrassing. 

The consensus amongst seasoned halo observers and professional photographers is that full frame cameras are largely free of this level of artefact or at least they are not affected to quite the same degree. However, sadly for many, myself included, professional full frame cameras are just too expensive and so we have to settle for cheaper consumer models. The problem here is that by and large you select a camera model based on a review you either see online or in a camera magazine. None of the reviewers who write these are engaged in the type of work we do so rarely, if ever, is this problem of artefacts encountered, mentioned or highlighted. Once a budding halo enthusiast has selected his camera on the basis of one of these reviews and splashes out several hundred euros on the latest consumer model, disillusion can very quickly set in when he realises he has bought a complete and utter duff. More than likely, he or she is going to be chained to this millstone for the next four or five years until they can afford something better.

So then, we come to the crux of this post: what to do about this situation? To all those who are in this situation and are experiencing this problem, I want to ask our readers two things.

Firstly, can we compile a list of camera makes and models that are particularly prone to artefact problems? I would like to do this to alert everyone to the problems with those specific models and to try to stop people wasting their money buying them if they are predominantly going to be used for photographing halos. This is not to say that a particular model is “bad” per se, just that it is ill suited for halo photography. Conversely, if you are in the fortunate position of being in possession of a camera which is particularly free from artefacts or one which you could recommend in this respect, we would also like to hear from you. 

Secondly, I would like to ask everyone whether they have any tips or solutions for overcoming or lessening these artefacts if you are unfortunate to have a camera that is beset by them. These tips could either be in-camera or pre- or post-processing. 

After a suitable period of time, once we have received some feedback on this issue, perhaps we can collate the results and do a follow up post. I would also be interested in posting particularly horrific examples of artefacts in halo photographs which would act as a warning to the curious. Please send any images or private correspondence to thehalovault@gmail.com.

Update

To clarify following enquiries, the above image is 8-bit and is used for illustration purposes only. In my experience, 8-bit are always unusable for this type of work. 16-bit are variable and one cannot predict when or why artefacts will appear. When they do manifest, they are every bit as unusable as 8-bit, at least with my equipment.

Trying to simulate arcs associated with parhelia in Rovaniemi solar display

Above is a display showing arcs extending outwards from parhelia and an attempt at simulating with Lowitz oriented plates using HaloPoint software. Sun elevation was 14.5 degrees.

In the lower right panel is a simulation with all rays. On the upper right is the same simulation (well, not exactly the same, ray numbers are a bit different) that shows from Lowitz orientation population only rays that experience 3 or 5 hits. This leaves the arcs from 325 and 315 type raypaths (the so called Schulthess arcs) visible while some others, such as Lowitz arcs are filtered out. The Lowitz arcs are seen in the lower left simulation, which has only rays with 2 and 4 hits from Lowitz oriented crystals.

The Lowitz arc scenario is clearly out of question to explain the arcs in the display, there is no match. Then how about the 3 and 5 hit scenario? Comparison is easiest with the flashing image below. The outer arcs fit together quite well but the inner ones don't. The inner arcs are angling too steeply inwards in the simulation.

Did I just do a botched job in matching the simulation to the photo? I admit it is not perfect work, but likely not so bad as to account for the large mismatch of the arcs.

Could it be because of the projection difference between the photo and simulation? I know that my 8 mm Sigma fisheye doesn't align perfectly with HaloPoint fisheye projections. For example, subanthelic arc is always narrower and taller in simulations than in photos. So maybe this too is just down to projection. Some day we might have a simulating tool that allows customization for individual lenses. That would settle the issue.

But even then we would still be long way off explaining these kind of displays. How do you get rid of Lowitz arcs in the simulation? I could not find a way. You have to really burn the Lowitz arcs to get 315 and 325 type arcs. This scorching inevitably gives also 46° contact arcs as is shown by the fuller version of the simulation below. In the fuller version of the photo next to it there are no signs of these arcs. Also, I was not able to simulate the correct length of the outer arcs. Lessening tilts seemed to make them disappear altogether. But I wasn't exhaustive in my attempts, it might have been possible to get them right.

What else? The display has no Kern arc even though cza was quite nice and diamond dust smooth. Clearly Kerns are not to be taken for granted. While observing, I thought there could be a chance here, but at the same time had a feeling that sun is probably too high, the plates too thin (you pretty much can say it without looking at a crystal sample) and tilting too much for the good old H.F.A.

Some words about the hunt itself  - the ryynäys as we say here. I was doing spotlight at the night and things got crappy as supersaturations increased. Diamond dust was everywhere but really poor halos. Expectedly it was no better in the morning. Close to the ski centre, diamond dust was so thick the sun did not shine through. At the edge of the cloud where the sun shone brightly there was quite some crystal glitter in the air, but, as it is with this glitter, it comes at the expense of halos: only pillar and subsun was visible. So I went shopping to a grocery store, hoping that in the meantime warming air brings a positive change.

It got better. However, the display was good only at the receding edge of diamond dust cloud. So I photographed in one place and when it weakened, hopped into car and followed the cloud to a new place to photograph again. I did six such manoeuvres, after which the swarm was soon done away completely by the heating sun. The photo shown here is the best set that I got at the third location.

Some technical info. The display was seen on 7 March 2017 in Rovaniemi. Temperature was probably around -16°C at the time I took the stack. It has 54 photos taken during 5m10s, starting at 10:13. Stacking was done with Registax 5.0. The artefacts seen in the image are a scourge of some series of Nikon cameras, they come in daytime photography and there is nothing you can do about them in post processing. 3000 series is one plagued with this issue (I have 3200 and 3300) and from what I have heard from other people's experiences 5000 series too. Definitely not cameras for halo photography.

Halo Phenomena in Olaus Magnus’s Historia de Gentibus Septentrionalibus (Part 1)

Parhelia in Historia de Gentibus Septentrionalibus, Bk. 1, Ch, 17.

This is the first post of a three-part series focusing on the rich material that can be found in Historia de Gentibus Septentrionalibus (History of the Nordic Peoples), a popular and influential work of the 16^th century. The work was written by Olaus Magnus and was printed in Rome in 1555. Soon after its publication, it was translated into several languages and thus became a “bestseller” of the age.

The author, Olaus Magnus, was a Swedish theologian, cartographer and writer, and the last Catholic archbishop of Uppsala. He maintained good relationship with King Gustav I of Sweden, and partly due to this, he was sent on various diplomatic and ecclesiastical missions around Scandinavia and other parts of Europe. During these travels he recorded his observations and what he had heard from locals, which later gave the basis of his magnum opus. When his country adopted the Lutheran faith, Olaus decided to remain loyal to his Catholic religion, and stayed abroad for the rest of his life. He was issued the title Archbishop during this turbulent period of his life, but the title was only a nominal one, as Olaus had been banned from Lutheran Sweden.

Historia de Gentibus Septentrionalibus is Olaus’s major work, which consists of 22 books divided into chapters, and is illustrated with 481 woodcuts. In his first book, he deals extensively with halos and dedicates 5 chapters to them. Of these, chapters 17 and 18 deal with parhelia and paraselenae. Olaus seems to have personal interest in these phenomena: when he lists occasions of three suns or moons visible in the sky, he mentions his own birthday at the beginning of October in 1490.

Olaus starts his description of parhelia by saying that in the North, around sunset and sunrise, they frequently appear at any location. They are white or rainbow-coloured, there could be two or even more of them, and are “never above or below the true sun, but at an angle to it” (All English translations by: Peter Fisher and Humphrey Higgens). As a 16^th century Renaissance scholar, he pays much attention to authenticating his writing, and supports his description by referring to natural historical works of Seneca (Naturales quaestiones), Pliny (Naturalis Historia) and even to the popular 12th century encyclopaedia Speculum Maius, written by the Dominican friar Vincentius Bellovacensis. Thus, in his explanation about the formation of parhelia he relies on earlier sources and theories, most of which would now raise a smile. Although the description is very far from the truth, we must acknowledge that some properties of parhelia are rightly observed. Already in the 16^th century it was realised, for example, that their formation is connected to clouds, more precisely to clouds that have specific thickness and uniform nature. 

Olaus Magnus’s description goes as follows: "(…) a parhelion is a rounded shining cloud, similar to the sun; for at the time of an eclipse we set out basins, which we fill with oil or tar, in order to observe how the moon stations itself before the sun, because a viscous liquid is less easily disturbed and retains the images which it receives. Therefore as the images of the sun and moon are viewed like this on earth, so also it happens in the sky that when the air is condensed and pellucid, it takes upon itself the figure of the sun; other clouds catch this up, too, but pass it on if they are moving or if they are thin or contain impurities. For the moving ones scatter the image, the sparse ones let it escape, while the foul and filthy ones receive no impression of it, just as with us things that are stained give no reflection."

A further interesting detail of the text is the idea that if a second parhelion appears in the sky, it is the mirror image or reflection of the first one; “clouds that present this effect are said to be dense, light, brilliant, flat and composed of compact matter.” He also states that parhelia cannot be seen on clouds very far from the sun because the beams of sunlight cannot be reflected from afar. Paraselenae (Chapter 18) depend on the Sun’s brightness as Olaus says, since the Moon “has no power at all to initiate action on inferior bodies, except for reciprocating and receiving light from the sun”.

Paraselenae in Historia de Gentibus Septentrionalibus, Bk 1. Ch. 18.

At the beginning of  Book 1, chapter 17, Olaus notes that the reason why he finds it important to talk about the phenomena is that locals believe they signify upcoming events. For farmers parhelia indicate rain coming. If the parhelia are visible in the South and they last long, farmers in the hills can sow seed safely. If, however, two parhelia are “contending” with one another on the sides of the real sun and then vanish, sailors must beware of severe storms. In wintertime, when there are three moons in the sky, they foretell snow, frost and cold.

By: Ágnes Kiricsi

Sources:

Olaus Magnus, A Description of the Northern Peoples, 1555, Vol. 1. Ed.: Peter Foote, Hakluyt Society, 1996.
Olaus Magnus, Historia de gentibus deptentrionalibus. http://runeberg.org/olmagnus 
Images: Lars Henriksson http://www.avrosys.nu/

Weak odd radius display on 09 March 2017

Yesterday in St Petersburg was an odd radius display with a predominance of plate forms.

The morning was cloudy. Around 11-30 sky started to clear. After half an hour the whole sky was covered high clouds. But I did not see any halos. It seemed it was usual bad clouds, which not produce halos. Nevertheless, in some moments I saw very weak and wide 22° halo with something resembles upper 23° plate arc. Also was an episode when I saw compact CZA, which apeared without parhelia. My suspicions have only become stronger, about that I faced with subvisual odd radius display.

It was brilliantly confirmed when I returned to home and processed stacks. I was able to identify such pyramidal forms as upper 9° plate arc (possible), upper 23° plate arc, lower 24° plate arc. Also were captured 9, 18, 20, 22, 24, 35 (very diffuse, link) and 46 halos. Odd radius halos lasted 50 minutes, until 13-30. Then until the end of display (until 15-30) were captured only weak common halos, such as upper tangent arc, parhelia and 22° halo.

It was fourth display since 15 February, which includes pyramidal halos.

Snow gun generated column display

On the night of 15th November 2016 (the night of the "supermoon") I was out of the city photographing the full Moon. The humidity was extremely high, which was evident by a huge aureola that was surrouding the Moon.

I was keeping an eye on webcams located at nearby ski centres, because the temperature was dropping below zero and snow coverage was scarce, therefore I was hoping for some snow gun action.

Few centres were operating the snow guns, but no diamond dust formation could be seen, so after a while I decided to return back to the city, but still keep an eye in case the conditions change. According to my previous post, Bílá ski centre is supposed to be the holy grail of diamond dust halos around here. But that is not true, there is another ski centre which generates diamond dust very frequently. I stayed up the whole night because I knew something would happen, and I was right, the ski centre I was talking about started generating halos, so I packed up my things and went again.

It is slightly further away than Bílá, so the trip took a while, but it was totally worth it:

This display, to my astonishment, was generated by a single snow gun (in the picture above it is located just behind the trees). No low hanging stratus, just high humidity and one snow gun. And it wasn't even on my previously planned location, it was actually a few kilometers ahead of it.

There are some indications of Parry oriented crystals, uppercave Parry is present and lowercave maybe too. indicated by a brightening on the circumscribed halo. Lowervex Parry was not seen. Wegener was maybe there, but the display itself was changing quite rapidly and I don't think my photos captured it.

Eventually I have decided to finish driving to my location. No halos there, and as I was returning, only faint and diffuse 22° halo was the only one left in the sky.

The crystal swarm was fairly thick, which can be seen in the main photo - the infralateral arcs were hanging in front of the forest. An amazing sight.

Fun addition: I had actually forgotten my gear at the location, and only realized it at home, so I had to return. It was still there!