Some diamond dust odd radii in Rovaniemi

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

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

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

        

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

The "leftovers" from the 23 November 2015 display in Rovaniemi

By Jarmo Moilanen, Marko Mikkilä and Marko Riikonen

In three previous posts we have dealt with different stages of the 23 November display that had some interesting features, like an anomalous Hastings/Wegener arc and a possible 4th Tape arc. Here we show the rest of the material we got that night.

After the lunar display was gone, wind direction changed and we followed the diamond dust to a new location. As usual, there is only one place to choose from when temperatures are not very low and the new field we found ourselves in was less optimal than the earlier one, having a rather confined space and yellow streetlights nearby. But you photograph where you can.

The image above and two below show that it was overcast again, moon glowing weakly through the cloud. In the beam, the display was not nearly as good as it had been before, yet it was by no means poor – it is only because we had been just a bit earlier spoiled by a monstrous halo complex we didn’t feel that inspired anymore. Add to that the ever more demanding calls of the land of slumber (we had been up most of the previous night and not sleeping in the daytime either because halos wouldn’t let us), we packed it all up and headed for the caressing warmth of the indoors even though the display was still kicking on.

                                                     Lamp elevation is around 0 degrees in the three photos above.

Who knows what there would have been on the offing after we gave up, there was still plenty of night left. As were about to doze off, the stratus clouds started breaking and moon shining bright again. Any change in conditions means also change in halos, and this one may have been for the better, judging from earlier breaking of clouds which produced a major spectacle.

In the image gallery at the bottom there are also photos from the first action of the night, soon after it was dark. Crystals were collected and there were plenty of plates with internal structures.