Sundogs

Sundogs, also known as parhelia or mock-suns, are optical effects caused by the glint of sunlight hitting millions of ice-crystals within the atmosphere. Ice crystals can be present in high-level cirrus clouds at any time of year, because of the coldness of the atmosphere at that height.

Sundogs are relatively common, but because of their proximity to the sun, they tend to go unnoticed, and often disappear within minutes. Usually they are relatively faint, but occasionally they may be bright. I photographed this sundog late last year, and to my great regret, it was brighter before I took the photographs!





In the middle image there is a faint vertical rainbow-coloured smudge near the power lines that is probably a fragment of a supralateral arc. You can read more about spotting and identifying these fascinating phenomena at Les Cowley's Atmospheric Optics site here.

If you're new to halo-spotting, read this page about the 22-degree halo first. Once you've found the 22-degree halo, finding other haloes becomes easier, and this page also has important information about protecting your eyes.

Cirrus streaks

I don't seem to have posted many cloud pictures lately, a terrible state of affairs! Here is some handsome wispy cirrus cloud. The first image also features the top portion of a 22-degree solar halo, visble as a bright arch in the middle of the image.

Fire in the sky

I took these pictures last summer. There was in fact no fire, just low, hazy clouds, lit by the setting sun.

[if it's real, scary exploding fire you want, try these pictures of Anak Krakatau (=son of Krakatoa). Thanks to Tom for the link]

Identified flying objects

Lenticular clouds have elongated, streamlined shapes. They are sometimes mistaken for flying saucers. Can you see why?!

I took these on Friday afternoon.















I took this one later on. As you can see, there was still a lot of iridescence in the sky.



More of my pictures of lenticular clouds here. More information about iridescence here. And there is a particularly good explanation of the origins of lenticular clouds and the iridescence that often accompanies them, here.

Mutant space jellyfish!

It's so tempting to look at astronomical pictures and find forms we recognise, or think we recognise, in the shapes of nebulae and dust clouds.
This is a very handsome view of the Carina Nebula. But tell me you don't see the mutant space jellyfish in this detail.

Crepuscular and anti-crepuscular rays

Crepuscular rays are areas of brightly-lit air that appear to radiate outwards from the sun when it is setting or rising. They are caused by clouds or mountains near the horizon casting shadows across the sky. Under good conditions the rays can be seen crossing the sky all the way to the point directly opposite the sun, the anti-solar point, where they appear to converge. In fact both the apparent divergence and the apparent convergence are illusions caused by perspective. The sun's rays are parallel but we perceive them as converging in the same way as we perceive a railway track as converging in the distance.

A full explanation, diagrams, and examples, can be found on Les Cowley's brilliant Atmospheric Optics site, here.

There was an amazing sunset here in Christchurch on January 17th. Clouds near the setting sun cast shadows across the sky that resulted in dramatic contrast between sunlit and shadowed air.

This was the view towards the sun:


This was the view to the north. You can see the rays' paths across the sky, travelling to the east...

At the anti-solar point in the east, the rays appear to converge. Around the anti-solar point these are known as 'anti-crepuscular' rays:

Crepuscular rays and anti-crepuscular rays are different ends of the same phenomenon, as can be seen in this wide-angle image taken of the same January 17 sunset at Birdlings Flat, some 50km from where I took my photographs.

I photographed a dramatic single crepuscular ray on April 5:

Photographic anxiety

You'd think that perusing stunningly beautiful photos of meteorological phenomena (http://www.atoptics.co.uk/) would be a nice soothing thing to do before bed, right?
Well, it gave me nightmares!

In the dreams I would see an amazing spectacle unfolding (mirage, halo, clouds, whatever) and reach for my camera. There are a number of ways this plays out:
1) I have left my camera at home
2) I reach for my camera but it is not in the case/bag
3) I have left the camera in the car, which is parked on the far side of a busy highway, which I have to cross (twice), Frogger-style, before I can attempt to take the picture. I think there was even a variant of this dream in which, having crossed the highway, I had lost the car keys, and could only look yearningly at my camera through the car window.
4) My camera battery is flat
5) When I press the shutter button nothing happens. This is actually the worst, since I can see the amazing scene framed by the lens, but can't record it.

In each scenario the amazing spectacle disappears unphotographed.

Do other people have these sorts of terrifying nightmares?? clouds