2009. december 30., szerda
2009. december 27., vasárnap
2009. december 24., csütörtök
2009. december 21., hétfő
"77 – The same day from 8 to 10am, Dobrowolski noted the parhelia, accompanied at 10am by a rainbow. At 11am he noted a halo. At midday : halo and rainbow. At 1pm and at 2pm : double halo. There was doubt about the cloud cover; thus at 8am we noted 4?, from 9am to midday 0?, at 1pm : 1?. Horizon misty. The morning a thin layer of low cloud, cirriform, moving quickly. In the afternoon at 1pm and 2pm the were some cirro-cumulus on the horizon. Temperature –13° at 8am, -9° from 11am to 2pm.
Here is a note I took at 1130am : Light westerly breeze. A little blowing snow but not much. The atmosphere was full of crystals, which, carried by the wind, scintillated [sparkled] in the air giving the impression of an infinity of gold and silver threads. We found ourselves in cirrus ; we saw it better towards the horizon, where there was a clearer aspect of mist. The halo phenomenon showed itself in a more complete form than usual. In figure 33 the outer circle represents the horizon, s the sun, z the zenith, h, h, h the fragments of the halo wth parhelia, p’, p’’ the fragments of the horizontal circle, a a rainbow as opposed to the halo, l’ and l’’ two fragments of the barely visible great arcs and finally c the arc of a circumzenithal circle. I measured the diametre of the halo h : 53° (radius 26° ; it is not therefore the normal halo). Distance from c to the zenith : 28 or 29°. The rainbow a covered 67° of the horizon and the base of the arcs l’ and l’’ we found about 30° from the extremities of arc a. The parhelia were clearly marked [visible], the same as the image of the sun on the horizon which was very bright (figure 34). There was no cross nor aureole. The fragments of the horizontal circle were like the fading lateral trails from the parhelia. The fragment of the zenithal circle (reddish, becoming white on the inside) were very interesting for the observer. We saw effectively that there were clouds of crystals [i.e many crystals] blown by the wind. It became apparent a short distance aloft of the BELGICA, because we could clearly see the gusts of crystals which passed it. Moreover, against the ships crow’s nest [lookout point up the mast] the wind produced a swirl and there it formed a little whirlwind which had a coloured appearance and which, like the circumzenithal circle, produced a bright trail. So, these phenomena far from being moved away from the observer, projected themselves as if they were a long way in the sky, while in reality they were very close to us. At about 2.30pm there were again traces of the morning parhelia and, as the atmosphere contained fewer crystals, the solar halo was very beautiful due to its variety of colours : the red inside, then orange, then yellow, the green and blue were visible. However, the coloured band was very tight [close together]."
2009. december 20., vasárnap
Diamond dust started falling around Himos, Finland on 14 December, and kept on for 4 consecutive days. This display with subparhelia was shot on the first day. A full parhelic circle was also observed, and for a short time, part of the subparhelic circle was visible, too ( 1 ). Marko Riikonen sampled the crystals during the display ( 2 ).
2009. december 18., péntek
Also visible are vague upwards curving extesions from Liljequist parhelia, which might have formed a complete half circle around subanthelic point if there was no cutting shadow. These are signs of the diffuse subanthelic halo that was photographed last winter in Rovaniemi ( 1 ). See also the lamp side of the display ( 2 ). The photo was taken by Marko Mikkilä in Sotkamo on 14th December. Click on the image to see a simulation.
2009. december 17., csütörtök
2009. december 16., szerda
2009. december 15., kedd
At the camera's LCD display the 18°/20° (?) and 35° halos could easily be seen. After first seeing them in the photo I thought I was able to see them visually too, but that was not certain. I did mess up the crystal sample, since the most-likely-pyramidal-crystals are distorted and round - the gear was still too warm during the sampling. On the other hand, if I would have waited longer, there would not be any signs of pyramids in crystal samples, since the pyramidal phase was gone in less than 10 minutes and did not reoccur during the rest of the night.
By clicking the image above the gallery opens.
2009. december 8., kedd
All of us are more or less skeptical about this explanation, but we think it deserves testing. The model predicts a strong lower 20° arc. We are asking that, if you are lucky enough to see an M-arc, then please put yourself in an elevated position and look for the lower 20° arc. There are other observing suggestions as well, but I think I will leave them for the blog.
2009. december 7., hétfő
2009. december 5., szombat
However, when darkness fell, the water fog cleared off and diamond dust started kicking in as the air got colder. In the beginning the moon showed no good halos but spotlight gave a reasonable display ( 1 ). Later also the moon halos catched on, as is seen above. Click on the image for more photos.
Simulation of the display ( 2 ) needed slightly flattened columns to get the subhelic arc intensity right. With any other crystal shapes, the part opposite to the moon where this halo is tangent to Tricker arc, was not visible. Intuitively those flattened crystals would take Parry orientation, so it looks like again we are not really understading it. Same effect was also present in the great Himos display last winter ( 3 ).
After midnight Mikkilä headed home because the high clouds in the background were becoming too disturbing. All together the halo hunting trip took 600-700 km of driving. Looking at the results it was definitely worth it. See also the photos by Jari Luomanen from the same night at the Sappee ski resort, and be sure to read his insightful description of the diamond dust formation on the right ( 4 ).
2009. december 3., csütörtök
Shown above is his most well known halo observation, the one with the "Arctowski arcs" that in the drawing rise from the horizon at about 120° from the sun. There are also other peculiarities, for Arctowski reports the patches of h to be 26 - not 22 - degree radius from the sun and the circumzenith arc distance from the zenith to be 28-29 degrees, which is probably more than it should be at the observation's sun elevation.
But if we leave the measurements aside and look at the drawing, the sunside of the sky looks pretty ordinary. The Arctowski arcs, which he writes as being faint, could be misplaced 46° infralateral arcs. And the rainbow in the opposite sky could be a fogbow. So, nothing extraordinary there, except maybe for the fogbow, that still has not been captured on film with halos in naturally lighted conditions.
Any French speaking readers here who could translate Arctowski's account of the display (PDF page 40-41)? It looks like he had made some interesting notes on the halos showing up in nearby crystals. I can add it here.
2009. november 30., hétfő
2009. november 25., szerda
46° contact arc is formed by Lowitz-oriented crystals and it divides in three components. One of the components comes from raypaths that pass through prism face that is parallel to the Lowitz axis. This component is found straight above and below the sun. In spinning crystals light ray can enter both prism and basal face (1-3 / 3-1 type).
Two other components (shown above for 0° sun elevation) are formed by raypaths that pass through prism face that is at an oblique angle to the Lowitz axis. They are distinguished by the ray either entering (4-1 type) or exiting (1-4 type) this face. These arcs are not in the solar vertical and their position changes with sun elevation.
See simulations (Jukka Ruoskanen's software) where 46° contact arc components are shown from spinning crystals for different sun elevations ( 3 - 4 ). Normally, though, halos from Lowitz orientation are not indicating spinning-type orientation distribution. Rather, we will see 46° contact arc from either plate-Lowitz or Parry-Lowitz orientation ( 5 ).
On most sun elevations 46° contact arc components conform deceptively the curvature of the 46° halo. Circumzenith arc also can overlap upper components. Because of the delicate form of 46° contact arc, it may be very difficult to observe in high clouds. Chances are certainly better in uniform diamond dust.
2009. november 24., kedd
2009. november 22., vasárnap
Once in similar situation also sub-120° parhelion and subanthelion was seen ( 2 ). If ice is thick enough, it is good take a little walk and and look around for these less conspicuous halos as well.
2009. november 20., péntek
Helic arc is no news in snow gun generated diamond dust displays, but in high clouds the halo is extremely rare. Of the latter type, shown here is the latest case. The display was seen in Alpharetta, Georgia, U.S.A, in 5 December 2008 and the photo was taken by Thomas Faber. Click on the image to read Les Cowley's notes on the display. There is also a simulation included.
2009. november 17., kedd
2009. november 16., hétfő
The photo was taken by Marko Mikkilä on 15 January 2009 in Sievi.
2009. november 15., vasárnap
Thus, the crystal wedge angle that makes the Moilanen arc does not seem to occur in plate crystals. Column oriented crystals seem to also be out of question, because in simulations for one thing this orientation would make also lower Moilanen arc, which has not been observed yet. And if we assume that some of the columns or plates take Parry orientation, it makes sense to conclude that Parry crystals are neither the answer.
So, it feels like Moilanen arc crystal makes no other halos at all, and finding the crystals from crystal samples should be easy. But we have looked at many samples already and there has never been anything peculiar occuring in great enought numbers to name as a suspect. It is also interesting that Moilanen arc has not been seen alone yet, which could imply that its crystal after all makes other halos.
It is mysterious, but one day somebody is bound to take those desicive photos. Displays that have common halos only from one crystal orientation (such as here) are of course the best ones to look for the crystal.
2009. november 12., csütörtök
Glenn Wolford photographed this display on November 9 in Syracuse, N.Y., U.S.A. The noteworthy feature is the upper Lowitz arc from Parry-Lowitz orientation. Click on the photo for simulation. Lowitz crystal tilts in the simulation are 13 degrees and sun elevation 30 degrees. Simulations and crystal figures from Jukka Ruoskanen's software. See also another photo ( 1 ).
2009. október 20., kedd
Text: Michael Ellestad
2009. október 19., hétfő
Starting from the 1970's we have seen numerous photos of subparhelic circle opposite to the sun and it is a little wonder that sub-120° parhelion has never been observed from an airplane. Even the sub-Liljequist parhelion, of which formation is sensitive to crystal shape deviations from regular hexagon, and which from that point of view should be rarer than sub-120° parhelion, has been photographed a couple of times.
Well, given enough time, things are bound to change. On 31 July this year sub-120° parhelion was finally photographed. The man behind the camera, Tomas Trzicky, was on a return trip from watching a total sun eclipse in China. The halo display appeared on the last stretch of this trip, on its last hour, when the airplane started descending to Prague.
"I was really lucky - actually I was sitting in the isle during most of the flight, one member of our observing group left her window seat for a while, so I more or less routinely checked the white haze outside - and there it was :-)", tells Tomas.
The sub-120° parhelion was captured on two photos, click on the image above to see them. To the left from the halo is a patch of subparhelic circle, which most probably is sub-Liljequist parhelion. Further left, in other photos, subanthelion and faint diffuse anthelic arcs crossing it are also visible ( 1 ). The window was dirty and it was frosty, but it just adds to the magic of discovery.
These photos may explain why sub-120° parhelion has not been captured earlier. It occurs as an isolated white spot, without subparhelic circle crossing it. Unless being exceedingly bright, it must be easily missed. Most certainly sub-120° parhelion has occurred in all of the displays with subparhelic circle, because plates are the major contributor to subparhelic circle intensity. Subparhelic circle made solely by Parry orientation is more of a theoretical consideration, and columns do not make subparhelic circle at all.
Sub-120° parhelion has been photographed once earlier in spotlight beam in diamond dust ( 2 ), but Tomas's "old school" observation is of course the true discovery. See also Les Cowley's report ( 3 ) on the case.
2009. október 18., vasárnap
It's been before our noses for a year already ( 1 ): the weak colored arc reaching far outside the 46° halo in the display observed on the night of 5/6 November 2008 in Rovaniemi. I have thought of it as some sort of 46° supralateral arc extension below the horizon. But something has not felt quite right with that and I finally decided to run a simulation.
The halo arises in column crystals from 3-5-1 and 3-6-1 raypaths ( 2 ). Thus it is not 46° supralateral arc. Rather, these raypaths make it a reflection of 46° supralateral arc. If circumnadir arc had been visible in the display, this halo would have been tangent to it ( 3 ) similarly as normal 46° supralateral arc is tangent to circumzenith arc.
The simulation above was made with column and random oriented crystals. Crystals towards triangular shape seemed to provide best overall fit with the photo. Light source elevation for the simulation was -11.5 degrees. The simulation on the right is filtered, showing some common halos together with the new halo arc.
What should we call this? Reflected (46°) supralateral arc or sub(-46°) supralateral arc? If we were to choose the former, the "Ounasvaara arc" ( 4 ) which arises from similar raypath (8-4-1) in Parry crystals, could be then called reflected (46°) Parry supralateral arc.
Simulations and crystal raypath figures are from Jukka Ruoskanen's software.
These simulations show the relation of blue circle (from random crystals) and blue spot (from oriented crystals). Blue spot on parhelic circle occurs where blue circle crosses it. The blue circle itself has a radius of 64°, as Ágnes Kiricsi has pointed out, and it is centered around the subanthelic point. Sun elevations in the simulations are 10°, 20° and 31°. When sun is higher than 32°, blue spot is no more seen. Simulations are made with Jukka Ruoskanen's software.
2009. október 8., csütörtök
This 22° halo on ice surface was seen on 17 January in Tampere. It was more pronounced on the right side. Intensity asymmetry was not caused by local changes in crystal densities because it was seen wherever I walked on the ice.
The effect must be made by atsimuthally oriented crystals on the lake ice. Possibly wind blowing from one direction had caused non-uniform deposition of moisture, resulting in (poorly) atsimuthally locked crystals.
See animation ( 1 ), which involves about 70 photos taken during 30 meters camera movement. The asymmetry effect is also seen in stacked image of 117 frames ( 2 )
This is not the first time when asymmetry of halos on ice surface has been noticed. In December 2007 Jari Piikki photographed curiously inclined halos in Juva ( 3 ).
2009. október 5., hétfő
Text: Michael Ellestad
2009. szeptember 4., péntek
Text: Claudia Hinz
2009. szeptember 3., csütörtök
Text: Claudia Hinz
2009. augusztus 28., péntek
MMT Observatory in Arizona has an automatic all sky camera that records the sky day and night. Archived videos are available from 2006 ( 1 ). Halos are visible in these recordings (although many displays are lost to the overexposure). Here are some examples:
- 22° halo / circumscribed halo. In the beginning possibly 9° halo ( 2 )
- Parhelion and patches of parhelic circle starting at 15:46 ( 3 )
- Parhelic circle starting at 13:58. Also 120° parhelion appears. The image above shows 60 seconds stacks of the display ( 4 )
- Parhelic circle appears at 21:15 ( 5 )
- 22° halo and some upper tangent arc, best starting at 02:00 ( 6 )
Ágnes Kiricsi, Marko Mikkilä and Mónika Landy-Gyebnár went through several months of the recordings listing the ones with halos ( 7 - 8 - 9 ). In ( 7 ) the best displays are pasted orange. Much of the MMTO Sky Camera material is still unchecked with regard to halos, certainly there are some decent displays to be found.
2009. augusztus 27., csütörtök
An avid atmospheric optics photographer, Pitan Singhasaneh has recently started experimenting with time lapse halo photography. Even though the displays are not special, the cloud movement and changes in halos create its own kind of magic. Pitan's videos are available at his Time-lapsed Photogaphy site ( 1 ). The photo above is from one of these displays, showing a 9° halo. If you like to see how halos in general look in the tropical climate of Thailand, see Pitan's photos from 2008 and 2009 ( 2 - 3 ).
2009. augusztus 25., kedd
2009. augusztus 16., vasárnap
This minor odd radius came with a surprise after stacking. Outside the 18° halo / plate arc there seems to be a faint, but rather well defined 20° column arc. As there is no sign of 9° stuff, crystals had no middle prism which is rather rare situation. The display was observed on August 9 in Kontiolahti.
2009. augusztus 13., csütörtök
There is a short PDF manual together with an explanation of how the halo is simulated. Finally you can download the (rather messy) Java source code.
Detailed (large recycle value) halos may take the order of one hour to simulate. With the least detailed (recycle = 1) setting it takes much shorter time.
There are two implementations of the halo applications, one for Macintosh OS X 10.4+ and one for Windows. A Windows machine may need to download the Java Runtime Environment (JRE) that is available free ( 2 )
Text: Lars Gislén
2009. augusztus 12., szerda
after consulting Jarmo Moilanen, who noticed the shadow of the airplane,
the halo was identified to be "only" a sub-anthelion with a short
sub-parhelic circle attached to it. No other halos were seen. ( 1 - 2 - 3 )
The halos were seen on a flight from Helsinki to Ivalo on July 21, 2009
at 17:40 local time, and they were visible only for approximately 10-15
2009. július 9., csütörtök
Click on the image to go Walt's page to download it.
2009. július 1., szerda
This display was observed on 1 July 2009 in Tampere, Finland. The most prominent features were the bright upper tangent arc (contributing to a partial circumscribed halo) and the parhelic circle. A faint Wegener arc can be seen rising above the upper tangent arc. The sun elevation was 46 degrees. More photos on Jari Luomanen's website (1).
2009. június 23., kedd
2009. június 19., péntek
2009. június 12., péntek
2009. május 27., szerda
2009. május 10., vasárnap
Text: Karl Kaiser
2009. április 14., kedd
Some of my own photos from Brannenburg, Southern Germany can be seen in an album or as a slide show ( 1 - 2 ). More pictures from other observers in West Germany, Austria, Switzerland and France are linked at spaceweather.com and in the German halo forum ( 3 - 4 ).
Text: Claudia Hinz
2009. április 6., hétfő
Text: Michael Ellestad