I saw this amazing circumhorizon arc around 1:30 this afternoon. I had just crossed the street while walking to lunch when I looked up, saw it…and walked back to the office to get my camera!

Lesson learned: always bring the camera!*

It started out as just a couple of small segments, but as the clouds drifted into position it quickly grew, and at its strongest it was just long enough to fill the field of view on my camera. There were also a couple of fragments of a 22° circular halo visible at the time.

The whole thing had vanished by 1:50, as the clouds drifted out of alignment, though I did see a more complete circular halo later on.

It looks like a sort of straightened-out rainbow, but it’s actually caused by ice crystals. If the right type of crystals cover the entire sky, this will actually stretch in a circle all the way around the sky, parallel to the horizon.

They’re a lot less common than the 22-degree halos. I’ve seen and photographed a ton of those over just a few years, but this is maybe the second time I’ve seen something like this. Fourth if you count the two feathery fragments I’ve seen.

At times like this, I really wish I had a DSLR, but the point-and-shoot will do in a pinch.

*On the other hand, when I went back, I pointed it out to a couple of people at the office who are into photography, since it was visible through the windows on one side of the building. One of my co-workers has a digital SLR and carries it with him, so he went outside and got some great shots. If I hadn’t taken a late lunch and chosen to walk anyway and been in the habit of looking for halos and forgotten to bring my camera, chances are no one in the office would have seen it.

Update (May 17): I just discovered that there are people who think these clouds are connected to earthquakes. No, they aren’t. They’re caused by ice crystals refracting sunlight, just like most halos, and have been seen in many places that didn’t have earthquakes.

A mosaic of four photos I took this afternoon of a full 22° halo around the sun. It was extremely hazy, and the halo was almost impossible to see without sunglasses because of the glare. I actually stopped the exposure down in order to get the halo.

A few minutes earlier (and a few miles away) I also saw a faint fragment of a circumhorizontal arc. Oddly enough, it was the same time of day, time of year, direction of the sky, and stretch of road as the last one I saw! If I drove that stretch of road regularly, I wouldn’t be so surprised, but I’m only rarely in that area at lunchtime.

Update: About a month later, I saw a really clear circumhorizon arc (or rainbow cloud)…from my office building’s parking lot!

I spotted a great 22° halo around the sun this morning, almost by accident. There was a reflection in the rear window of the car in front of me that looked like it could be a distorted contrail or it could be a distorted halo. Once I parked, I looked — and there was this clear halo, almost 3/4 of the circle. The missing quadrant was to the lower right, so I just framed this to get as much of the visible part as I could.

It wasn’t really this blue. The G1 tends to make images in daylight a little extra blue, and seems to have really gone overboard on this one. I’ve got to remember to bring the regular camera with me more often!

While driving around lunchtime, I saw an airplane pass overhead, its contrail casting a shadow on the thin cloud layer below. I had my camera handy, and was stopped at an intersection, so I snapped a couple of shots. As often seems to happen, the first, haphazard one was the best.

The diagonal line extending down from the sun is, I believe, a sun pillar-like effect in the trails left by the windshield wipers. Also: Unless I’m mistaken, you can just barely see the edge of a halo in the feathery clouds at bottom center. It’s the slight reddening.

A few hours earlier, I saw this:

I glanced out the window while changing lanes on the freeway this morning & noticed the bottom edge of this halo. By the time I had a chance to stop the car and really look, the lower arc seemed to have disappeared, but the left side was sharply visible – as was a sundog. I rolled down the window and snapped a couple of photos while waiting for the light to change. Unfortunately, I couldn’t position anything to block the sun, so the exposure isn’t all that great.

By the time I reached my destination and parked, it had all faded except for a slightly bright patch in the clouds to the left.

What surprised me is that the halo was not only still there after lunch, but clearer. On the way back, I stopped in several places with a building, or a sign, or a tree blocking the sun. The curve seemed too shallow to be a standard circular halo, so I wondered what I was actually seeing. Then I realized there was a faint halo inside the brighter curve, the two fragments meeting above the sun and splitting like diverging roads.

Then I noticed the sundog.

Three distinct sun halos. Not complete, and far from the clearest display I’ve seen, but certainly the most complex.

The brightest part appears to be the top of a circumscribed halo, which varies in shape from oval to kidney-bean depending on how high the sun is. You can just see the 22° circular halo branching off below it. Off to the right is a sundog.

It’s too bad I only had the phone, but it did manage to catch all three halos. I fiddled with the contrast a little to make them clearer, but they are visible without it.

And to think I saw this from the middle of suburban Southern California!

A complex display of crepuscular rays lighting up a haze of smoke drifting in from the Station Fire.

This next shot, taken from a 4th story window, isn’t framed as well, but shows off the complexity better.

Sun Rays 2, originally uploaded by Kelson.

Sundog, originally uploaded by Kelson.

Friday was a good day for atmospheric optics. I watched a sundog for most of my drive home.

Tree Halo, originally uploaded by Kelson.

Yesterday morning while driving to work, I looked up from the road and saw two parallel lines in the sky: One white, one dark blue. They were, of course, a contrail and its shadow on a thin cloud layer below. Because it was a thin layer, I started looking (when I had the chance) for fragments of halos.

When I finally stopped the car, I took a picture of the contrail and its shadow (now nearly aligned with the sun), looked up and saw a faint edge of a halo. I moved a bit to the left, putting a tree in front of the sun, and there it was: a clear 22-degree circular halo centered on the sun..

We stopped the car, found a tree to block the sun, and both looked. There was so much glare it was easier to see with sunglasses on, so I lent mine to Katie so she could catch it. Finally I grabbed the camera and took a few pictures, most of them using a gate post instead of the tree.

We ran some more errands, and I caught up with her at the grocery store. On my way from the car, I looked up and saw a perfect bright sundog to the right of the sun, much brighter than the clouds around it and showing the full red-to-blue spectrum. I should have gone back to the car for the better camera, but I used my phone camera instead, and got this shot.

I got to the edge of the lot just as Katie was leaving, and immediately said something like, “Look! Right above that palm tree!” Then I took off my sunglasses, realized that it was completely washed out without them (though it seems to have come out all right on my cheesy phone camera), and handed them over again. It continued to be visible, though less well-defined (it was a lot sharper than this photo shows) for at least half an hour.

A circle around the sun, and a bright rainbow-colored spot in the sky. I wonder how many people walking around never even noticed.