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Some elementary stuff. Although there is high cloud, light snowfall made the sun pillar. In the evening there was moon corona. Took a hdr set and worked it with FDR-tools, which is good for coronas.
2010. december 21., kedd
Floodlight helic arc on 15/16 December 2010 in Tampere
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This one was seen from automatic gas station lights. The helic arc is rises diagonally from the lamp. I was desperately looking for a place for the spotlight, but the surroundings were totally light polluted. Just 300-400 meters away it was totally dark wilderness, though, but the diamond dust never reached there. So I just photographed the halos in this light. I walked closer to see if I could see 3D structure in helic arc, but as expected, it disappeared. The tangent arc had no seagull shape at the appropriate lamp elevation, indicating presence of Parry arc, which certainly was there. The helic arc is doubled because there are two lights.
This one was seen from automatic gas station lights. The helic arc is rises diagonally from the lamp. I was desperately looking for a place for the spotlight, but the surroundings were totally light polluted. Just 300-400 meters away it was totally dark wilderness, though, but the diamond dust never reached there. So I just photographed the halos in this light. I walked closer to see if I could see 3D structure in helic arc, but as expected, it disappeared. The tangent arc had no seagull shape at the appropriate lamp elevation, indicating presence of Parry arc, which certainly was there. The helic arc is doubled because there are two lights.
2010. december 20., hétfő
Spotlight display 15/16 December 2010 in Tampere
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This one came as an almost complete surprise. I had seen moment before parhelia from streetlight when driving, but they were weak. The pillars were almost non existent, so when I parked at the hospital area and turned on the long lights, I was surprised to see the crystals glitter in the beam in a very much all sky display manner. This was confirmed as I walked the beam.
Taking on the spotlight took some time and I did not get much photos. There was also serious light pollution. Just a bit further away towards the lake it would have been darker, but you have to take the first photos where ever the display is, or you risk not getting photos at all (this wisdom Luomanen told me recently).
Simulations of the display are made with Jukka Ruoskanen's HaloPoint 2.0. The most interesting point to me is the 5 degree rotational Parry population that had to be used to get the intensity of the diffuse B arc right. Nothing new here, of course, this kind of effect is pretty common in the spotlight displays. Lessen the rotation and they turn into subanthelic arcs. The Parry population makes also right kind of brightenings at Tape arc locations. Should they be called Tape arcs or 46° supralateral arc, is probably a matter of taste.
In simulation the subhelic /helic arc (they overlap at 0° light elevation) is too intense as always. Perhaps the Lefadeux hollowed crystal simulations could fix it. I have included also simulations showing the diffuse anthelic arc A and B components (well, actually they are independent halos), which are clearly discerned in the photo. In sun displays these are less easy to distinguish, which is why we normally talk only about the diffuse arcs.
Temperature was around -22° C. It is rather unusual to get column (or Parry) stuff at these temps.
This one came as an almost complete surprise. I had seen moment before parhelia from streetlight when driving, but they were weak. The pillars were almost non existent, so when I parked at the hospital area and turned on the long lights, I was surprised to see the crystals glitter in the beam in a very much all sky display manner. This was confirmed as I walked the beam.
Taking on the spotlight took some time and I did not get much photos. There was also serious light pollution. Just a bit further away towards the lake it would have been darker, but you have to take the first photos where ever the display is, or you risk not getting photos at all (this wisdom Luomanen told me recently).
Simulations of the display are made with Jukka Ruoskanen's HaloPoint 2.0. The most interesting point to me is the 5 degree rotational Parry population that had to be used to get the intensity of the diffuse B arc right. Nothing new here, of course, this kind of effect is pretty common in the spotlight displays. Lessen the rotation and they turn into subanthelic arcs. The Parry population makes also right kind of brightenings at Tape arc locations. Should they be called Tape arcs or 46° supralateral arc, is probably a matter of taste.
In simulation the subhelic /helic arc (they overlap at 0° light elevation) is too intense as always. Perhaps the Lefadeux hollowed crystal simulations could fix it. I have included also simulations showing the diffuse anthelic arc A and B components (well, actually they are independent halos), which are clearly discerned in the photo. In sun displays these are less easy to distinguish, which is why we normally talk only about the diffuse arcs.
Temperature was around -22° C. It is rather unusual to get column (or Parry) stuff at these temps.
2010. december 19., vasárnap
Spotlight Moilanen arc and windshield subparhelia
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Some stuff from the night of 11/12. December 2010 with Luomanen. We took replicas of the Moilanen arc display, but they failed. Could have been an enlightening case. On the windshieldd there was also parhelic circle, cza, cha - the usual stuff. Luomanen is holding the lamp.
Some stuff from the night of 11/12. December 2010 with Luomanen. We took replicas of the Moilanen arc display, but they failed. Could have been an enlightening case. On the windshieldd there was also parhelic circle, cza, cha - the usual stuff. Luomanen is holding the lamp.
2010. december 18., szombat
Halos from Mustavuori snowguns 12 December 2010
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Mustavuori snowguns made this display. Some driving around and quick stops were involved as the diamond dust changed its location. Moilanen arc occurred on two stages, better second time. The photos of it above are 101 and 120 seconds stacks with 43 and 52 frames respectively. Crystal sample was taken, but too late, the display started soon vanish as I got the dish out. There were not much crystals in the sample and nothing special shows up in the two photos.
There is faint helic arc but no Parry arc (not even with heavy usm). Helic arc occurs pretty much in any diamond dust halo display. It has been seen even with sun pillar only. The question is what kind of helic arcs these non-Parry occurrences are? Do they arise from the same angle as Parry helic arc? If not, how many different helic arcs there are? Should probably compare this one with simulations, it comes out pretty strong with heavy usm (checked that, it has the same angle as normal helic arc).
The photos with sun in it has a pretty strong overexposed area. I have had Nikon D70 for about 5 years and this has always been the problem. Only now I realized that blocking the sun is the cure for it. So, in the future photos there will always be blocker. Actually, it is good to stack even the smooth diamond dust displays. Earlier I did not think it would help much, but it does.
Mustavuori snowguns made this display. Some driving around and quick stops were involved as the diamond dust changed its location. Moilanen arc occurred on two stages, better second time. The photos of it above are 101 and 120 seconds stacks with 43 and 52 frames respectively. Crystal sample was taken, but too late, the display started soon vanish as I got the dish out. There were not much crystals in the sample and nothing special shows up in the two photos.
There is faint helic arc but no Parry arc (not even with heavy usm). Helic arc occurs pretty much in any diamond dust halo display. It has been seen even with sun pillar only. The question is what kind of helic arcs these non-Parry occurrences are? Do they arise from the same angle as Parry helic arc? If not, how many different helic arcs there are? Should probably compare this one with simulations, it comes out pretty strong with heavy usm (checked that, it has the same angle as normal helic arc).
The photos with sun in it has a pretty strong overexposed area. I have had Nikon D70 for about 5 years and this has always been the problem. Only now I realized that blocking the sun is the cure for it. So, in the future photos there will always be blocker. Actually, it is good to stack even the smooth diamond dust displays. Earlier I did not think it would help much, but it does.
2010. december 16., csütörtök
Hole punch cloud 14 December 2010 in Tampere
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I went to check the diamond dust even though it was cloudy. There was nothing, as expected. I was reporting in the phone to Luomanen the situation when hole punch cloud caught my attention. The Ac was probably the slowest moving I have ever seen and there was plenty of time to photograph this. Much different from the other hole puch a few days earlier in Hervanta, which moved and changed really fast. I have never seen hole punch clouds before and now two cases in the row!
I went to check the diamond dust even though it was cloudy. There was nothing, as expected. I was reporting in the phone to Luomanen the situation when hole punch cloud caught my attention. The Ac was probably the slowest moving I have ever seen and there was plenty of time to photograph this. Much different from the other hole puch a few days earlier in Hervanta, which moved and changed really fast. I have never seen hole punch clouds before and now two cases in the row!
2010. december 9., csütörtök
Column crystals halos on 8/9 December 2010
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Halos from column orientation were the main feature of this night in Tampere. In the beginning I was looking at the display with Luomanen but we did not have cameras. The display sort of took us off guard, it was thickly overcast and temperature at -5 C. Anyway, Y-pillars were visible in Hervanta and we got crystal replicas at least. Closer to the streelights beautiful circumscribed halos appreared, but it looked like there was some tilt involved. Columns with hollow ends in the replicas.
Later I continued on my own and took photos under streelight near Mustavuori. Took also crystal photos - the crystals have become more equidimensional (the temp also had dropped to -7 C). Plenty of triangles (the photos above are all from this live sample) which probably have been falling in Parry orientation but Parry was impossible to distinquish under the lamp. Certainly triangular thick plates do not take plate orientations because there was no sign of plate halos in this display. Kern from triangular plates is only theoretical consideration.
For the last I went back to Hervanta where I photographed the Y-halo from the police training area floodlight. Also helic arc is visible. At some place there was also parhelia. The display lasted several hours and who knows how long it had been going on before we entered the scene.
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