1876 Denver-Boulder display lays claim to the first reliable zenith arc extension and 44° parhelia

The appearance of the sky on Saturday, December 23d, will be historic. At least those who saw the heavens then from eight o'clock till two, will long relate the scene as one of the things most wonderful. — The Boulder County News, 29 December 1876

On Saturday, 23 December 1876, a halo complex occurred over the Denver-Boulder area that challenges the Saskatoon display of 3 December 1970 as the holder of the first reliable observation of zenith arc extension and 44° parhelia. Two accounts, written for separate publications by Sergeant James A. Barwick of the U.S. Signal Service at the Denver station, provide a strong case for these halos having been in the sky, not just artefacts of the mind that had crept in after the fact.

 

An after-storm display in a hard arctic outbreak

The display was the product of a massive arctic outbreak, and on the preceding night the area was in the grip of a blizzard: "Denverites need not be told about Friday night's storm, but for the benefit of non-residents THE NEWS will state that for several hours it was one of the worst known in this city," writes the Rocky Mountain News in 27 December issue.

Come morning, the show was visible right from sunrise. After describing the storm, the RMN article continues: "Yesterday morning the sun rose clear but the air was filled with particles of frost, the refraction from which caused the appearance of 'mock suns', or 'sun dogs'." Another article, in the Colorado Banner 28 December issue: "The air is filled with frost, reminding one of a snow storm...". So this was, as expected, diamond dust.

Yet from Barwick's newspaper account in the Boulder County News (29 December issue – said to be copied from an original in the Denver Tribune, but the issue is not available online) one might infer instead a cirrostratus sheet. Barwick writes that on "Saturday morning the sky showed a dull milky appearance," and then puts the display ending at 2:45 in the afternoon because that was "when the clouds became too thick to permit the rays of the sun being reflected or refracted."

Alas, Barwick seems to have been influenced here, at least on the morning part. Elias Loomis's Treatise on Meteorology (1873) – which Barwick in the same article names as the "Signal Service text book on meteorology" and which he says "has been very largely drawn upon for the explanation, causes, etc., of the occurrence of the optical phenomena above described" — carries, in its section on 22° halo, a strikingly similar phrase: "When the sky is hazy, and presents a dull, milky appearance…"

As to the afternoon thickening, I could find nothing in Loomis that Barwick might have drawn upon. Interestingly, the snippet in the epigraph, which is about the action in the 40 km distant Boulder, contains vague parallels with Barwick's afternoon remarks: "At least those who saw the heavens then from eight o'clock till two..." Then again, the full text from which this comes from, continues to describe a blazing parhelion after the sun had already gone behind the hills:

As the sun fell behind the hills, the lower end of the upper and western quarter of this brightest ring was all that remained; but that point seemed in all its colors even more brilliant than before, as it stood on the face of the high front hill at Gregory Cañon like a prismatic sun doing its best in honor of the coming Christmas. 

Even if the timing of sun falling behind the hills is dependent on the observers position relative to the hills, this feels like an observation further down in the afternoon, because around 2 pm the sun was still quite high.

Now, while Barwick gives an impression of high cloud origin for the display, he also has language that is suggestive of diamond dust: "The air on Saturday being calm and still, these snow crystals descended slowly to the Earth." But this is said in the context of explanative talk on crystal orientations, so doesn't seem to be an observation of the actual conditions. And again, it looks like it's not really Barwick talking here, because in Loomis the section "Parhelic Circle" has similar and in part identical wording: "When the air is tranquil, the flakes of snow which are present in the atmosphere descend slowly to the earth…" More of Professor Loomis will be seen creeping into Barwick's account below. 

But I would rather not get lost in the fog of conflicting accounts here, because the big picture is in any case clear: in this kind of outbreak the high-cloud-bearing systems have already swept through ahead of the front, and what is left behind is the cold dome itself, with a clear upper atmosphere And this outbreak was one of the hardest the area has known, for the very next morning, Sunday the 24th, Denver fell to its second-coldest temperature on record, −25 °F / −33 °C (https://www.weather.gov/bou/lowtempextremes).

Solar elevation change in Denver on 23 December 1876.

Three newspaper accounts of the display. The one on the left tells of the storm. The one in the middle – a more learned piece – interestingly seems to take pains twice over to leave no impression that any full zenith circle was seen ("…an arc of another circle" and "This circle, or rather arc of a circle…"). Yet I don't see it throwing in doubt the Barwick's full circle. Perceptive abilities differ between people, some being infatuated by the brightest features to the extent that they fail to see any fainter ones. The left-hand article appeared in RMN daily of 24 December and weekly of 27 December; the middle one in RMN daily of 31 December and BCN of 29 December 1876. On the right is a cursory description of the display in the CB December 28 issue. It would be of interest to find the man behind the erudite "J. D.", who reaches for the observations of the ancient philosophers and Hevel's famous display.

 

The Boulder County News, 29 December, has a massive section containing three accounts of the display, Barwick's taking the lion share.

The zenith arc extension

On to the actual business. The zenith arc extension already comes out compelling in Barwick's Monthly Weather Review account (Vol. 4, Issue 12, p. 8, December 1876): "That portion of the zenithal circle (SS) which lay nearest the sun, was a strikingly brilliant rain-bow, the red being nearest the sun, and all its glowing colors were very clearly defined." This tells us the zenith arc was not merely extended to a uniform full circle afterwards – the circle consisted of two distinct parts. The reading is further bolstered by a note at the end about a second display, seen on 10 December at Pembina, in Dakota Territory (now North Dakota), which is credited with only the rainbow segment of the circle.

But the most striking evidence is in Barwick's newspaper article:

When the sun had reached an altitude of 12° above the horizon, a brilliant arch in the form of an inverted rainbow, represented by the letters S S, was seen to form a tangent with the halo of 46° radius C C, at its highest point above the sun. As the sun rose higher in the heavens this arc became more curved, and between 9:40 and 11:50 a.m. it had formed itself into a complete circle of about 15° or 18° radius. One-quarter of the circle was of the most brilliant and glowing colors, showing the different colors of the rainbow, so very distinct that they could be traced one after the other, from red, nearest the sun, to violet, which was farthest from the sun, the centre of this arch was the centre of the zenith, observed from where the observer stood. The remainder of the circle was distinct enough, but did not show any of the prismatic colors, and was not so wide as the portion where the colors were so distinct.

I have had goosebumps many times over my halo career, but reading this moved me for the first time to tears. And yet – is Professor Loomis's shadow looming over Barwick here too? For it is not only the falling-crystals passage and the "dull milky appearance" that Barwick took from him. The mangled tangent arc in Barwick's drawing (NN, OO) echoes Loomis's own diagram, in which two elevation forms of the tangent arc float slightly detached from the 22° halo. And Barwick has the zenith arc appearing only once the sun reached 12° elevation – precisely the figure Loomis gives (erroneously) as the lowest possible elevation for the halo. Moreover, Loomis writes of reported parhelia at 50° and 98°, of which Barwick duly notes the latter as visible in Denver (HH, alongside the 120° parhelia LL). I could cite more similarities, but enough. So was I an old sentimental fool for those tears? Actually, I am starting to get paranoid. What if Barwick didn't even see the display and his two reports are simply pure Loomis channeled through him?

Not so fast. Loomis gives not a word nor a drawing of any zenith arc extension. The only pre-Denver observations of the extension I know of are those of Dufay's in Paris on 6 March 1735 and J. W. Lambert's in Wetzlar, Germany, on 24 January 1838. To be in the know, Barwick would in practice have had to be reading Bravais, which has these, yet he cites only Loomis as his source.

Barwick's piece in Monthly Weather Review Vol. 4, Issue 12, p. 8, December 1876. It's the first halo display drawing and proper report appearing in this January 1873 launched journal. Until then only listing of halo observations across the country interspersed with occasional, short details were published. The Pembina display could be worth tracking down.

 

Loomis's diagrammatic presentation. Note the similarity of the slightly detached tanarc shapes (a, a') to Barwick's drawing.

And even if, for argument's sake, we grant that Sergeant Barwick had read the French of Bravais, or perhaps had parleyed with someone in the know (J. D. most likely, who wrote in RMN and BCN), we still run into the problem that neither of the two earlier observations resemble what he describes. Neither Dufay nor Lambert reports the dual feature – a bright, colourful zenith arc with a fainter white extension. Dufay's is a uniformly colored circle (though gapped opposite the sun); Lambert's is, oddly, a uniformly white one. Bravais does also carry a theoretical note on the possibility of a multiple-scattering extension, but I cannot see that transforming easily into Barwick's description either.

Turn instead to modern displays in which the extension has been reported visually, and we find two brethren to Barwick. Ripley and Saugier, in the Weather article "Photometeors at Saskatoon on 3 December 1970", describe a white extension in the display. In the second modern visual I know of – the display of 29 February 2016 at Klaukkala, Finland – Marko Pekkola writes of having seen Kern arc as a "faint, fragmented, suggestive glow," but gives no indication of colour perception (in the photos the arc is quite distinctly coloured, https://www.taivaanvahti.fi/observations/show/49209). And in the third case – the Saskatoon-class Siziwang Qi display of 14 February 2020 – of the two persons who reported seeing the extension, Tian Xiangyang and Zheng Dan, the former called it coloured while the latter recalled a "mostly whitish arc all around" (from personal communication with Jia Hao).

So while absolute certainty is probably beyond reach, I judge it unlikely that Barwick knew anything of the zenith arc extension. His describing the dual nature of SS was where Loomis momentarily relaxed the possession of him, letting him set down the extension, true as it stood in the sky.

44° parhelia 

The parhelia at the crossing of the 46° halo and the parhelic circle are pictured and discussed in Loomis's book – most insightfully, as will be shown below – so they, too, could have found way into Barwick's account without having actually been in the sky. But the photographed displays tell us that in a supermassive diamond-dust show of this kind carrying the zenith arc extension, the 44° parhelia (which at higher sun elevations would rather appear as 46° parhelia) are as a rule part of the package. So long as we accept the zenith arc extension real, we can count in also Barwick's XX parhelia, despite him not giving any helpful details on the feature. 

Until now, I have regarded Saskatoon display as the first reliable documentation of 44° parhelia. The halo was photographed, so there is no question whatsoever on the veracity. However, my skepticism towards the earlier would-bes is not for the lack photos – a non-photographed observation is fully acceptable as long as it meets the standards. And the pre-Saskatoon reports of parhelia on 46° halo just don't meet the standards for 44° parhelia. Most observations are in high clouds, which automatically renders them highly suspect for the reason that no high cloud 44° parhelia have been photographed. And the diamond dust ones neither survive a closer look for whatever reason. Below I have provided two historical diamond dust examples that fail to convince with their parhelia on 46°.

The drawing by J. R. Blake of one of the diamond dust displays in his book "Solar Halos in Antarctica" looks the part for 44° parhelia. But reading the account pancakes it. Blake describes both parhelia on concentric halos as very bright – an impossibility regarding the outer ones if one supposes they were 44° parhelia. As for the arc at the zenith, Blake was in the know of the Kern arc possibility, but is not saying a word about it in the display description. Clearly, in his mind this was something different. The location ("passing through or close to zenith") of course doesn't match, but neither do the other aspects ("fairly bright coloured arc... the colours being very distinct"). The date for the display is 29 November 1958.

 

In the likely diamond dust display on 1 February 1882 in Fort Conger, Ellesmere Island, parhelia spots were placed at the crossing of 46° halo and parhelic circle. But these are suspect from the get-go because similar spots are drawn at almost all crossings. The identical character of these mock-moons in the written account reinforces this interpretation: "Six mock-moons were present, two on either side of the true moon, and two above it, all of which showed brilliant prismatic colors, very like the clear, distinct colors seen in rainbows." The display is really a model case of the scourge of completionism. The distant mock-moon on the left is described as having been at 90° azimuth and white. The display is found on page 186-187 in "Three years of Arctic service : an account of the Lady Franklin Bay Expedition of 1881-84, and the attainment of the farthest north, Vol I", written by Adolphus Greely. The signature of F. Leblanc belongs to the French wood engraver who hand-carved the printing block based on an original field sketch of the display. He was not a member of the expedition.

 

How Denver zenith arc extension fits into the historical picture?

No camera was turned at the zenith arc extension in the Saskatoon display, it was hinging only on the drawing and description by Ripley and Saugier, fuelling endless speculation among enthusiasts. At least in Finland, no two halo people ever met without asking themselves, in hushed voices: "Did Saskatoon have Kern?"

But after the first photographed extension materialized from the stack Marko Mikkilä made of the 17 November 2007 display at Sotkamo, Finland, the possibility of Saskatoon really having contained the extension began to gain foothold. Fresh observations piled on more weight and finally, a visual sighting backed by photographs in the Saskatoon clone at the Siziwang Qi area of northern China (https://thehalovault.blogspot.com/2020/02/intense-kern-arc-from-china.html) settled for good the question of whether a zenith arc extension can be intense enough for visual.

The Denver report by Barwick moves the first reliable detection of the extension almost a century back from Saskatoon. The jump actually pushes 19 years past H. F. A. Kern's "original" observation of 8 October 1895 at Loenen aan de Vecht in the Netherlands, making this highly doubtful (and possibly even faked) report lose even more its standing, and rendering the case for using a name other than "Kern arc" stronger.

The 44° parhelia ride along with the extension. This possibly pushes Denver past all diamond dust displays that have parhelia depicted on 46° halo.

The drawing of Saskatoon display from the Ripley and Saugier Weather article "Photometeors at Saskatoon on 3 December 1970". The similarities with Barwick's drawing go even as far as using a thinner line for the zenith arc extension. My blogpost "The Saskatoon display" has some photos: https://submoon.wordpress.com/2011/01/24/the-saskatoon-halo-display/

 

Miscellaneous notes

With the significance of the Barwick's Denver sighting laid out, a word on some other issues in and around the display.

Denver-Boulder and Saskatoon similarities

The parallels between the two displays are clear for all to see. Both were unusually long-lived, starting at sunrise and going well over midday. According to Ripley and Saugier, in Saskatoon the show kept going for around five hours until about 14:30. The Denver-Boulder display was possibly lasting all the way till the sunset.

The compositions match too. Set aside the misplaced tangent arc in the Denver drawing – possibly a non-existent Loomis import – and the two are identical but for the sun elevation in the drawings. Both even carry the dubious extra parhelia between 44° and 120° parhelia.

On the naming

In the world of halos, extensions (one halo continuing another) are everywhere, and I see "zenith arc extension" — or "circumzenith arc extension" if you prefer the longer form — always a legitimate neutral choice to run alongside the observer name (with optional specifications of single-scattering plate, single-scattering Parry and multiple-scattering domains). My nomenclature article has a section on the zenith arc extension naming, which I have for convenience prepared into a post here in The Halo Vault: https://thehalovault.blogspot.com/2026/07/on-zenith-arc-extension-naming.html The text sets out the Dufay's extended zenith arc, which is one and half century earlier than Kern's, as the more convincing case of the two, thus raising the possibility of calling the halo rather "Dufay arc" than "Kern arc". In my X posts I have experimentally done exactly that, hard as it has been, having basically grown up on "Kern." But that's just when you have to steel your jaw and push harder; comfort zone is no place to be when halo naming problems need fixing.

And now Barwick has arrived on the block, and one thing he certainly does is to make the "Kern arc" even more unearned. Where there was one more convincing observation of a date earlier to Kern's, now there are two, the "Kern arc" growing ever more uncomfortable choice by it. But the high confidence level of Barwick's extension makes the ground unsteady also under "Dufay arc".

About daytime cold in Denver-Boulder

Denver and Boulder residential areas sit between 1500 and 1700 meters at a relatively low latitude of 40th parallel, so sun tends to warm the daytime air appreciably. Even so, in winter the temps stay below freezing on number of days. In Denver this averages at 21 days, and the coldest daily maximum on record – 3 February 1883 – was as low as −10 °F / −23 °C. When such a deep freeze sets in, it is not difficult to imagine diamond dust persisting until afternoon and even to sunset.

For comparison, the Siziwang Qi banner display on the Mongolian Plateau seems to have lasted all day. I don't remember where exactly within that area it was photographed, but the whole administrative region, lying between the 41st and 43rd parallels, ranges from 1000 to 2100 m in elevation, comparable to Denver-Boulder. Enthusiasts have for some while understood the high plains as the home for the most supermassive diamond dusts, and these days photographs of several displays a winter seem to come out of the Mongolian Plateau.

Two picks from Loomis

Not only was the Denver-Boulder display revelation to me, but also Loomis's book was a fresh acquaintance that delivered the goodies. It's with those that I finish this text.

In the section for the 46° parhelion, Loomis argues that crystals with vertically oriented prism faces (the alternate Parry orientation) would be unstable, and concludes that such a halo is better explained as parhelion of parhelion: 
 

These parhelia are probably produced by rays which have experienced the minimum deviation in the same direction in two vertical prisms, in which case the total deviation of the rays would be double of that produced by a single prism. Upon this hypothesis the parhelia should not exactly coincide with the 46° halo, but for elevations not exceeding 30° the difference might easily escape observation. The observations are not sufficiently precise to decide whether this explanation is admissible or not. 

Is Loomis the first to recognise the mechanism in plate-oriented crystals? Bravais conceived of multi-scattering through 60° prism in two crystals of the same orientation, but strangely considered only column and random orientations (far as what I have gathered from the book).

The second point of interest is Loomis's attempt to explain the Hevel's halo. He invokes the triple-alternate raypath 3-5-7 in triangular crystals, saying it produces "an illuminated surface of 92° radius, and having a tinge of violet on the side next to the sun." Today the feature we mainly associate this raypath with is the relatively common blue edge or blue arc at 87° from column oriented crystals, the equivalent and similar looking random-orientation feature being a much rarer catch. Is Loomis in fact touching here upon the blue-edge mechanism?

Loomis's text on the triple-alt raypath in triangular crystals to explain the Hevel's halo. He seem to imply in the first sentence, however, that the idea is not his. Did Bravais consider this?

Elias Loomis (left) and James A. Barwick. There is some info on Barwick in "History of weather observation. Sacramento, California, 1849-1948" by Glenn Conner. https://repository.library.noaa.gov/view/noaa/1202

Marko Riikonen

On zenith arc extension naming

The text below is a copy of a section from my halo nomenclature article published earlier this year (https://thehalovault.blogspot.com/2026/01/on-halo-naming.html) that deals with historical zenith arc extension observations and naming issues. I have it here as a post because I thought it might be useful companion for my upcoming post about a quite remarkable old display. I have quietly corrected a handful of typos. Two bigger changes are marked with asterisks and explained at the end.

*    *    *    *    *    *    *    *

And so on to the naming of the arc observed by H. F. A Kern in Loenen aan de Vecht, Netherlands, on the morning of 8 October 1895. In the original report in the Dutch weather amateur's Onweders Optische Verschijnselen circular (1896), it is opined that "Earlier observations in which this arc is mentioned are doubted, because in most cases the imagination of the observer clearly emerges from the report" (the original text shown in the illustration below). I know only two older observations, and the other one, dating a century and half prior to Kern's, doesn't, in the light of the current knowledge, quite fall under that remark, at least in comparison to Kern's. This is the display by a Frenchman of the name Dufay in Paris, on 6 March 1735.

                                                             H. F. A. Kern's observation in Onweders.

All photographed high cloud zenith arc extensions – to date 6 displays – have been in big displays, and by that standard, H. F. A. Kern's display comes out oddly light weight. Ignore his arc and what's left is just the zenith arc and 22° halo. Elsewhere in the country nothing of consequence was seen either. The best was at Gravenhage, where additionally parhelia and 22° tangent arc was reported.

In contrast, Dufay's Paris display is already a multihalo. It's five halos against Kern's two. The little details – the slight asymmetry of zenith arc and its extension combo, the zenith arc not being in minimum deviation position, and the one-sidedness of the 46° halo * – add to the observation's street cred. It also contained parhelia, which is expected in a zenith arc extension display. It is also interesting to note that in none of the high-cloud-six (Jutland, Kissimmee and Reading x 4) the extension appears as a separate segment on the opposite side. The extension is faint in many of these displays, but the general picture is rather a one of continuations of the zenith arc than a separate arc – just like is the case with Dufay. (This in itself is admittedly strange as it suggests highly triangular plates and a persuasive line of evidence exists for not supporting high-triangulars taking stable plate orientations).

Two displays containing an extended circumzenith arc predating H. F. A. Kern. On the left by Dufay, on the right by J. W. Lambert on 24 January 1838 in Wetzlar, Germany. In line with his drawing, Dufay writes the zenith arc encompassed more than half a circle. Curiously, Lambert reported the whole circle AB as having been white. A particular detail in Dufay's drawing is the zenith arc grazing the 46° halo: "Le rouge de l'arc tangent touchait le bleu du halo extraordinaire". Bravais regarded this with significance as it backed up his theory of circumzenith arc against the other theory, the top 46° contact arc, which would always be fully embedded in 46° halo. In his book, Bravais comments on this observation on page 103. H. Ekema mentions Lambert's display in his Maandblad voor Natuurwetenschappen article, writing: "In the rich collection of observations included in his treatise [Bravais' book] there is only one case that somewhat resembles the phenomenon at Loenen, namely on 24 January 1838 at Wetzlar Lambert observed a white circle around the zenith at a solar elevation of 20° 15′. Whether both observations truly relate to the same phenomenon is, however, doubtful."

In Onweders, Kern's display is given an explanation by a raypath in plate oriented crystals that we notate as 136, which, as the text goes, makes a fainter copy of the circumzenith arc opposite to the zenith (in Optische Verschjinselen aan de Hemel (1957) Visser refers to the H. F. A. Kern's observation, and has the arc alternatively called as "de gespiegelde circumzenithale boog"), covering the same azimuthal span as zenith arc, about 120 degrees at the display's sun elevation of 8.75 degrees. The theory seems to originate from one H. Ekema, who presented his calculation in a parallel article in Maandblad voor Natuurwetenschappen, 1896, No. 5 (it has recently come available on Google Books). Aside from the calculation, it repeats much of what is said in Onweders.

Today we have the benefit of simulations to know that while 136 makes an arc weighted at 180 degree azimuth from the sun, it is also exceedingly faint. The raypath that we are concerned with when looking at any single scattering display photograph of zenith arc extension, is 135. It is by far the dominating raypath in any realistically shaped plate oriented crystals and makes an arc that leaves a gap opposite to the zenith.

To be true, the raypath 136 for zenith arc extension is strengthened, to a varying degree depending on the crystal shape and light elevation, by similar raypaths 13457 and 13537. But the combo of these three raypaths still comes weak next to 135. Unlike 136, the two longer raypaths may not be perfectly opposite-weighted because they can have, depending on the crystal shape, an intensity drop at the opposite position and even an outright gap.

Plate zenith arc extension in three different crystal scenarios at +8.75° of the Loenen aan de Vecht display. All crystals h/d 0.4 dev 0.1. Regular hexagons and full triangles are without basal face shape variation. The intermediate crystal shape of the middle row has variation, shown is the average shape. 13537 in the middle row is not empty, just a meagre few dots. Zenith arc raypaths and raypaths similar to it (such as 13573) are not included.

But having the raypath wrong is not the issue here. It is simply that Dufay has an earlier observation that is more competent than Kern's.

And I can't shake off the feeling of Kern's observation being purposely faked. The observation is just too convenient. As if the theory of the gespiegelde circumzenithale boog came first and then an observation was concocted around it. But if it was fabricated, surely they would have taken care to include the parhelia, right? In his article, H. Ekema understands that the crystals required for the zenith arc and its extension also make parhelia, but manages to put a positive spin on the lacking of parhelia in Kern's observation by brushing the issue under the carpet and instead noting that parhelia were indeed reported in other localities that day. So maybe the Kern's arc was a real feature in the sky – but not a halo but a funny cloud.

I guess there is a difference on how to regard, in a historical drawing, an extension that is continuous from the zenith arc and an extension that is separate. The former may have come about because of the typical phenomenon of drawing things longer than they actually were. Supposing the continuation was not real (which must be true in majority, if not all cases; in none of the six visual was gotten) such completionism may have been unintentional – it's harder to remember things when you jot down your impressions hours, days, weeks or months later. The latter is harder to reconcile with this psychology. Here, if it wasn't something that the observer actually saw (a halo or funny cloud), the other option is intent fabrication.

Examples of completionism. On the right a display by Schult on 27 March 1826 in Oslo. Wegener arc reaches the sun and circumscribed halo is interpreted as two full circles. On the left a display by F. Lebland ** on 1 February 1882 in Fort Conger, Canada. There are a number of cases of parhelia drawn at the junction of 46° halo and parhelic circle. Many are likely due to completionism, though other explanations may also apply, one being 46° infra- and supralateral arcs giving an impression of weak parhelia at their crossing with the parhelic circle. Here also 44° parhelia is a prospect because this was most likely an ice fog display.

Of course it is possible that at some point a name has been so long around that it's now indifferent to attempts of correcting wrongs. So the Kern arc may be here to stay. The man goes by the full name of Hendrik Frederik Anton Kern, and he was 30 years old at the time of the observation. He trained as a teacher and settled in Loenen aan de Vecht where he became the headmaster of the primary school. He doesn't seem to have been that much of a halo man. I have copies of all the Onweders Optische Verschijnselen halo sections from 1896 to 1952 observations, but except for his 1895 observation, I don't recall having seen H. F. A. Kern's name in them. But he must have been specialized in other kinds of observations because he is listed as one of the observers in Onweders Optische Verschijnselen 1938 issue, which is the only digitized OOV currently available (not on a Dutch but Indonesian institution website, mind you). Possibly he was an onweders chaser. It would be worth perusing the full OVVs to see what kind of stuff he reported.

But should someone prefer to start using the Dufay arc, I see it as a legitimate name. Possibly his is the first zenith arc extension ever reported. Which is of course an additional merit, because, as I have already said above, naming arcs after silver or bronze medalists is bad practice (I am brushing here of course under the carpet the issue of common practice of naming halos after persons who have never observed them).

Dufay probably went by the full name of Charles-Francois de Cisternai du Fay – a scientist whose main bread was electricity. Or would it be necessary to consider a double name because Dufay starts his account by telling that he observed the display with Mr. Condamine (most likely Charles Marie de La Condamine)?

Actually, there is the option for keeping both Kern and Dufay. The Parry orientation born zenith arc extension is different from plate born extension in that it is not a full circle but an arc, with more than 180 degree circumference. And the Dutch theory, 136 in plate oriented crystals, draws an arc identical to the Parry orientation born arc – both are from raypaths in which the exit face is opposite to the reflection face. So if the single scattering plate born extension would be Dufay, Kern could be reserved for the special case of Parry born extension on the basis of the theory, even if the orientation is not the same (no other raypaths contribute to zenith arc extension in Parry crystals). But shouldn't the arc in that case be named after its theoretician – the Ekema arc?

For the multiple scattering version I see Ripley-Saugier and Bravais as person name candidates, the former for their observation in the Saskatoon display, the latter for his theoretical genius to envision the possibility of MS extension. This is found on page 99 in Bravais' book Memoire sur les halos. He discusses the azimuthal span of the zenith arc and writes: "However, it may happen that the theoretical amplitude is exceeded, and even that a complete circle is formed: 1) because each point of the arc gives rise to the formation of a parhelic circle, and because all these secondary parhelic circles, by superimposing themselves, can produce an appreciable light" ("Cependant il peut arriver que l'amplitude théorique soit dépassée, et même qu'il se forme un cercle complet: 1) parce que chaque point de l'arc donne lieu à la formation d'un cercle parhélique, et que tous ces cercles parhéliques secondaires, en se superposant, peuvent produire une lumière appréciable"). Bravais also mused on the secondary parhelic circle at 22° to explain observations like the one by J. W. Lambert shown in the illustration. It's a certain mammoth in the room that Bravais does not have a halo named after him. True, the zenith arc has been called 'Bravais arc' in some writings, but I don't hear it used today. Which I think is good because by tradition person names are for more special halos. There is also a third MS halo that could be named after Bravais, the 44° tangent arc, which he also wrote about in his book.

Marko Riikonen

* in the original this reads unintelligibly "one-sidedness of the extension"
** the original credits this to F. Lebland, which is a double mistake. First, it is F. Leblanc. Second, he was not on the expedition; he was a wood engraver who prepared the printing block based on a sketch that someone had made of the display. The display appears in "Three years of Arctic service : an account of the Lady Franklin Bay Expedition of 1881-84, and the attainment of the farthest north, Vol I", written by the expedition leader Adolphus Greely.

A divergent-light 22° halo from a Long March 6A reentry

Around 19:51 (UTC+8) on 4 June 2026, the RedNote user "岚烟喵喵喵" (ID:6109395002) photographed a bright divergent-light 22° halo at Qishui Bay, Hainan (19.6416°N, 110.9883°E). The light source was probably the reentering stage of the Long March 6A (Y25), which shone through high clouds about twelve minutes after lifting off from Taiyuan Satellite Launch Center at 19:39. The strong divergence made the 22° halo appear noticeably distorted rather than circular (Fig. 1). No precise orbital data was available for the reentering stage, thus an approximate trajectory was reconstructed from the government maritime navigation warning (Qiong Navigation Warning 82/26)¹ and from image fitting. 

Fig. 1 Frame 300, showing the divergent 22° halo

The trajectory reconstruction here is rough. No aerodynamics are used. It is a purely geometric back-projection with drag and reentry deceleration ignored, so this is an approximate trajectory. There is only one viewpoint, so the direction to the source is constrained but its distance is not. And the fit was done by eye, so errors are large.

The observer was located at Qishui Bay from terrain in the video and the RedNote post, with a small cove ahead of them matched against Google Earth to find the coordinates (19.6416°N, 110.9883°E) as shown in Fig. 2. Because the event was at night and low over the sea, no calibration stars were available, so the camera was calibrated against the terrain instead. SRTM 30 m DEM data gives the three-dimensional coordinates (latitude, longitude, height) of the surrounding landscape. Manually aligning the terrain outline visible in the video, the two small hills on the left, with the DEM-rendered terrain solves for the camera's field of view and pointing. Once calibrated, any pixel in the frame can be converted to an azimuth and elevation.

Five pixels along the glowing track were measured this way, giving five sightlines. The debris is assumed to move along a straight line in space. However, single-station angles cannot fix the distance scale. The official drop zone was therefore used as the trajectory endpoint, and the distance to the debris at each of the five points was then solved by least squares. The fitted points have a collinearity residual of about 1.3 km, which is small compared with the roughly 200 km range, although it should not be interpreted as a formal uncertainty. The result places the glowing reentry low in the east-southeast, at roughly 70 to 34 km altitude and 230 to 195 km away. This still rests on the assumption that the path is a straight line.

Fig. 2 Google Earth view of the observation site, matching the terrain in the video

The light passed through a layer of high cloud between the observer and the reentry. Himawari-9 cloud data for the nearest time (11:40 UTC) in Fig. 3 shows the sightlines crossing cirrus with tops around 13 to 15 km and an optical depth of roughly 0.5 to 1.4. This supports the presence of a suitable high-cloud layer.

Fig. 3 Himawari-9 cloud-top height at 11:40 UTC 

The parallel-light halo data was generated with ZHANG Jiajie's Lumice, and the divergent-light display was then computed from it using Lefaudeux's method². Because of the poor quality of the original video and the presence of only a 22° halo, the simulation used a single regular hexagonal crystal habit with a c/a ratio of 2.5. Several simplifications should be noted. The simulation accounts for neither the brightness of the light source nor that of the halo, and the optical transmittance of the cloud plays no role in it. The ice crystals are assumed uniform throughout the cloud layer, which was set between 13200 and 14700 m, with a maximum simulated distance of 300 km from the observer. The result is therefore meant only to show that the halo geometry matches the video, not as a precise photometric comparison. As can be seen in Fig. 4, the simulation aligns fairly well with the observation. 

Fig. 4 Frame 303 with the simulation result

Elevation 10.37°, distance 195.8 km

In divergent light, the crystals that can send 22° halo rays have positions that form an elongated cigar-shaped locus between the eye and the source, known as Minnaert’s Cigar⁴. A flat cloud layer therefore cuts this locus in different ways depending on the source elevation and distance.

Divergent-light halos from natural high cirrus are rare; a case illuminated by a rocket reentry seems even more unusual. A closely related case was published very recently by Haussmann³, in which a bright fireball produced a 22° halo whose radius was shrunk to about 20° by divergent effect. In that case, however, the source was near the zenith, so the cirrus layer cut Minnaert’s Cigar almost straight above and the halo remained circular, only smaller. Here the source was low in the sky, so the cloud layer cuts the cigar obliquely. This is the slanted-cut case that Haussmann³ pointed to as probably not yet observed, and it distorts the halo rather than simply shrinking it. It should be noted that no measurement as accurate as Haussmann's was possible here, since there was no simultaneous parallel-light halo in the same frame to serve as a reference. 

The Hainan event is only one of many possible divergent-light configurations. As the source elevation, distance, and halo type vary, the Minnaert cigar is cut in different ways, producing shapes that have rarely or never been recorded. To show how sensitive these forms are, I include a few simulations below.

Fig. 5 shows an animated 22° halo with the source at 30 m distance and the cloud top at 100 m, the cloud base rising from 0 to 3 m, and the elevation set to 0°. The halo shrinks into a "light ball".

Fig. 5 22° halo, source distance 30 m, cloud top 100 m, cloud base rising from 0 to 3 m

Fig. 6 shows odd-radius halos, with an elevation of −1°, a distance of 100 m, and a cloud layer from 0 to 5 m.

Fig. 6 Divergent odd-radius halos

Fig. 7 shows the diffuse halo of raypath 3-5-6-7-3, at elevation −25.6°, distance 100 m, and a cloud layer from 1 to 30 m. The halo takes two forms, one surrounds the whole horizon, the other looks like a normal diffuse halo. Here the cigar subtends such a large angle that it looks like a "tomato" (Fig. 8). Raypath filtering was applied.

Fig. 7 Divergent diffuse halos

Fig. 8 A "cigar" with a radius of 140°

All these examples assume the crystals are arranged in infinite flat layers. In reality the crystals can be distributed in very different and interesting ways, such as on windshields, where the halo shapes depend dramatically on the lamp elevation and the windshield's position between observer and source⁵. Marko Riikonen has captured many such windshield cases, including elliptical halos and reflection-view displays⁶.

An interactive HTML file is provided, allowing the simulation to be viewed together with the video, with tools to let the user experiment with the Minnaert's cigars. The original video and the simulation images are also included in the link.

https://drive.google.com/drive/folders/1Z8f5_HufUhPua_f9Rq92FNDS316jD3Cz?usp=sharing

Acknowledgements. I thank the Chinese halo community for help in reaching the original poster, Sedimentary-Cloud (沉积云) for help with the divergent-light simulation, and SONG Xi Pei for help with the rocket data. The original video is used with permission from the observer. AI assistance was used in programming and some other parts of this work.

References

¹ Qiong Navigation Warning 82/26, Maritime Safety Administration of the People's Republic of China (Qinglan MSA), issued 3 June 2026. https://www.msa.gov.cn/html/cnmsa/hxaq/article/2026/808345637af44bf3831ab02000ecc176.html

² N. Lefaudeux, "La simulation des halos divergents / Divergent light halos simulation", opticsaround, 27 July 2013. https://opticsaround.blogspot.com/2013/07/la-simulation-des-halos-divergent.html

³ A. Haussmann, "Divergent light effects in ice crystal halos created by fireballs: a case study of a 22° halo with a 20° radius," Appl. Opt. 65, C42–C47 (2026). https://doi.org/10.1364/AO.582021

⁴ J. O. Mattsson, L. Bärring, and E. Almqvist, "Experimenting with Minnaert's Cigar," Appl. Opt. 39, 3604–3611 (2000). https://doi.org/10.1364/AO.39.003604

⁵ W. Tape, "Windshield Halos," in Streetlight Halos (2010), Chapter 13. https://scholarworks.alaska.edu/uaf_mathstats_facpubs/3/

⁶ M. Riikonen, "26/27 Jan 2026, Rovaniemi… elliptical halo," X. https://x.com/RiikonenMarko/status/2016261603444793506

Mikkilä's Soul in high cloud

Hello from Japan,

On March 28, I observed an anthelic pillar while flying over Wakayama in Japan. This was unexpected, as there were no reports from the ground that day of anything other than a 22° halo. Four stacked images were created from 71 photos captured over a three-minute period.

17:29:26–17:29:35 12 frames  ave USM

17:29:39–17:29:59 10 frames

17:30:03–17:30:27 22 frames

17:30:28–17:30:53 23 frames

Aircraft altitude: 9,000 m; Sun elevation: 8.71°

At first, I thought this was a diffuse arc, but it did not match the simulation, as shown below.

As I pondered, I came to think of Mikkilä's Soul as a possible answer.

Another one was Robert Greenler’s alternative Parry orientation model. Let us consider this first, as it can be simulated easily.

An appropriately tilted alternative Parry orientation produces a pillar that is brightest at the anthelic point.  If we assume that the upper part is missing owing to the absence of cirrus clouds, this pillar appears to be consistent with the observations to some extent.

That said, this explanation is unrealistic. Assuming this is Mikkilä's Soul, I first tried to identify the diffraction fringes. However, neither B-R nor BGR showed any fringes. I also checked the single frames to rule out possible misalignment in the stacking process, but the results were the same.

 

The length of this pillar is 20° ± 1°, which raises the question of whether Mikkilä’s Soul can really be this long. The answer lies in the 2021 Åre display. If the Soul extended to the subanthelic point, it must have been at least 20° in length.

thehalovault.blogspot.com

Since there is no other plausible explanation, this can be considered to be Mikkilä's Soul. 

The Soul is virtually unknown in Japan and has never been observed there before. This could be the first observation.

 

Now then, does the Soul really shine brightest at the subanthelic point? The image below shows the moment the Soul’s brightness peaks at the subanthelic point. However, it seems even brighter somewhat below the anthelic point.

Is this simply due to the cloud’s unevenness? In the fourth image, both the subanthelic and anthelic points are clearly located within the same cloud. Further understanding of the Soul requires simulation.

 

As a side note, on August 19, 2025, I photographed a 120° subparhelion along the same flight path.

Supreme light pillars ('city maps') - 2026.5.3, AnQing, China.

 Between 23:00 and 24:00 (UTC+8) on May 3, LIU Qian Yu(刘乾煜) captured a supreme light pillars event occurring within high-level clouds(or falling virga in middle-level) in Anqing City, Anhui Province, China. The clarity of the observed 'mirrored city streets' map' is very very distinct and remarkable. JIA Hao and I consider this record to be among the most outstanding documentations of such phenomena worldwide. 

BGR+USM

As an experienced astrophotographer and member of the Chinese ice halo community, LIU promptly switched to an circular fisheye lens, thereby capturing a full view of this sky wonder. A meteorological chart corresponding to approximately three hours offset from the time of photographic observation is attached, with our appreciation extended to QIAN Kun for supplying this chart. 

Song Xi Pei contributed to the comparative works between LIU's image and maps.

I used Google Maps and Tencent Maps respectively to compare with the perspective transformed image.