Monday, 30 May 2011

New book on halos

The Finnish Astronomical Association URSA has just published a new book on halos by Marko Riikonen. This book combines the latest halo science with stunning images from all around the world.

Spanning 168 pages, the book presents, illustrates and analyses all the known (and the less well known!) halo forms in great detail. In addition, the newly made discoveries and methodologies concerning spotlight displays are discussed in depth. Many historical displays are also included as a reference. Particular care has been put into preparing the beautiful computer simulations that are used to explain the ice crystal populations behind each display.

The variety of the images is striking and Riikonen has obviously spent a lot of time in finding great examples. Luckily the quality of printing matches these images: I have rarely, if ever, seen a print job this good. Even the faintest halos can be distinguisted in the images.

As Riikonen is a long-time expert in the field, the substance of the book is solid and provides everybody from beginners to experts with new insights about halo science. Being such a significant contribution to the field of atmospheric optics one can but hope for a quick release of an English language edition.

A few select pages can be previewed online (1). Publisher information (2).

Riikonen, Marko (2011) Halot. Jääkidepilvien valoilmiöt. [Halos. The optical phenomena of ice crystal clouds]. Tähtitieteellinen yhdistys URSA ry, Helsinki.

Liljequist superparhelia & a nucleation agent gun

This Liljequist superparhelia was observed in the spotlight beam on 5 January 2011. The lamp is about a degree or two below the horizon, thus giving the central stage to the Liljequist superparhelia. The Liljequist parhelia can be seen against the snowy ground below the superparhelia.

The halos were seen in diamond dust that was generated by my water ice nucleation agent gun operating ca. 1 kilometer away from the site of the observation. The nucleation agent gun can operate autonomously for hours since the water supply is automated. The temperatures varied between -22 and -27 degrees Celsius.

The image above shows some colour artefacts (the background sky is not even color) as we were also testing Riikonen latest HID lamp (Marko Riikonen accompanied me during this night) that has two high intensity discharge bulbs. Unfortunately we were only able to fire up one bulb. Two bulbs would have produced a more even beam in terms of colours and luminosity.

Full image gallery is available (1). It also contains a lengthier account on the evening.

The nucleation agent gun can be seen in action in a separate photo gallery (2).

Atmospheric optics meeting of 2011 in Finland

Finnish Atmospheric optics enthusiasts met on 27-29 May 2011 in the Artjärvi observation centre. The topics of the presentations varied from the latest scientifical results in NLC research and simulation of higher order rainbows to the polar expeditions and observations of optical phenomena in the 18th century. The full programme is available (<a href="