Primary & Secondary Fogbows A lamp generated fogbow imaged in Finland by Jari Luomanen (atmospheric photography) on August 25, 2009. ©Jari Luomanen, shown with permission.
In summer there are no ice crystals for the beams of the Finland high intensity halo lamps to illuminate. Not to waste them, Jari Luomanen and Marko Riikonen shone them into night time fog to create a series of exquisite fogbows and glories.

Here is just one. Inside the bright and almost colourless primary fogbow, ranks of stronger hued supernumeraries march inwards towards the centre where they become a glory. The ‘Brocken Spectre’ is Jari Luomanen’s shadow cast through the nearby fog as he tends the tripod mounted camera.

Unusually, beyond the primary there is a fainter secondary fogbow and beyond that the secondary bow's supernumeraries. In sun created fogbows the secondary is rarely seen because of lack of contrast with the bright background. Sun generated secondary supernumeraries are a very rare sight on a rainbow and those on a fogbow are too faint and diffuse to compete with daylight.

The quality and number of supernumeraries depends also on the droplet size distribution of the fog. Near monosized droplets are best. Fog conditions changed often during the night vigil.

Magicians conceal their methods while scientists reveal their better magic. At right, a cold insulated Jari is illuminated with blinding intensity by the HID (high intensity discharge) lamp off frame to the left. He points the camera directly away from the lamp to capture the fogbow created by lamplight scattering by nearby fog droplets. The lamp casts his shadow onto distant trees. In this image by Marko Riikonen the shadow has no surrounding glory because that is only seen when looking directly away from the lamp.



Atmospheric
Optics

About - Submit Optics Picture of the Day Galleries Previous Next Today Subscribe to Features on RSS Feed
  

    

    

Marko Riikonen imaged by Jari Luomanen. A section of Jari's fogbow is visible - Marko's is not.
Jari Luomanen photographing his fogbow as imaged by Marko Riikonen. Each camera or eye sees only its own fogbow and glory and therefore Jari's shadow in this image does not show one.