Storytime 27

long exposure star trails over Jordan Lake
I’m running a little behind today, since I normally have the storytime post up by now, but I wasn’t feeling very well last night and had several other things to tackle. But it’s not like I’m being audited or anything. I don’t think.

full resolution inset of above frameThe main image above comes from just barely over nine years ago, taken July 3rd 2010 out over Jordan lake. I’d had some decent success getting images of the Milky Way while facing in the opposite direction, which were much darker skies, but decided for a longer exposure star trail. The exposure time was 559 seconds, which is slightly curious – that’s nine minutes, 19 seconds, and I usually aim for round numbers. I might have cut the exposure short thinking that a plane was going to enter the image – note the bright spot within the trees at right. Anyway, the residual city glow from the area was too bright and the effect wasn’t too compelling, but I stuck it in the folders anyway.

And then, looking for images to use last night, I noticed something, and so I’m including this full-resolution crop to show it as clearly as I can without very specific contrast adjustments. Because there’s a curious pillar of light rising from the horizon, and it goes way the hell up in the sky.

[While we’re examining the photo, of course, we’re going to completely ignore the red and blue spots that come from sensor noise – this is the old Canon Digital Rebel, the first iteration, and it never performed particularly well in this regard, but long exposures in digital tend to suffer from sensor noise anyway and I had the ISO boosted way up, plus I never did the noise reduction trick on this frame.]

Anyway, see the thin stream of light coming from the horizon and stretching up? That is, I believe, what’s called a sun pillar when it occurs during the day, but they’ve also been observed on particularly cold nights with streetlights and so on. I’ve caught the former before, but not the latter, or at least never realized it. The idea behind a sun pillar is, high altitude ice crystals that sit pretty much flat, parallel to the ground surface, reflect light back down to the viewer, so they act like a million tiny mirrors of bright light sources, but because of their orientation it only occurs in a line straight up from the source (more or less of course – when it occurs with the sun, there’s no ‘straight up’ that applies to orbital positions, but from our egocentric perspectives it’s close enough.)

You might think that July in NC wasn’t going to produce ice crystals, and it wouldn’t down at our (egocentric) level, but it doesn’t take a lot of altitude for the air to thin enough that ice forms easily. I’m more curious about the very distinctive single pillar, because I would have thought the sheer number of light sources in the middle distance would have produced lots of them, and cannot think of any particular source that differed so noticeably to produce the pillar. I could see nothing of it while I was out there that night, and indeed missed it several times over when sorting and examining the images for possible retention, but it’s clearly there, and by playing around with sliding the image back and forth, I can see vestiges of it that extend well up into the frame, at least as far as I have cropped right here – it may not be as easy to see on your screen, but that might be because you’re doing something incredibly silly like looking at anything at all on my site with a smutphone and not a proper desktop computer.

I know almost precisely where I was standing for that shot, and can plot a fairly accurate line of sight on a mapping service to see what might lie along that line, but I’m not sure how much that might tell me – again, I have no idea what kind of light source might be so different, and of course nothing of the sort will show up on maps. The best I can hope for is to see something different along the line, something that either sparks some recollection or makes me believe there are distinctive lights there, but I’m not counting on it being so easy. Still, that’s the kind of idle investigation that I get wrapped up in at times, so perhaps we might see an update a little later on.

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