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Combining 15s interval whole-sky-camera photos to form a 4y spanning keogram

531 点作者 nebalee5 个月前

27 条评论

isoprophlex5 个月前
This is fantastic, and like another commenter mentions, a beautiful continuation of an age old practice: measuring the sky.<p>Very cool that their hardware keept chugging along for years without hiccup, too.<p>If you want to do something kinda similar but far less involved: a very lo-fi, no computer involved thing to do is an ultralong photographic exposure (months, a year, longer) with a pinhole camera.<p>The results are quite artistic IMO [1], the camera is fire-and-forget and you don&#x27;t need any chemicals to develop the image. Just photograph&#x2F;scan the photographic paper and invert the colors.<p>I&#x27;m not affiliated with them, but Solarcan sells ready made single-use pinhole cameras. An almost zero-regret purchase I&#x27;d say.<p>[1] You see the sun move through one year of skies, as seen from my balcony: <a href="https:&#x2F;&#x2F;files.rombouts.email&#x2F;IMG_6500.jpeg" rel="nofollow">https:&#x2F;&#x2F;files.rombouts.email&#x2F;IMG_6500.jpeg</a><p>People have made wonderful, mildly spooky pictures with these: <a href="https:&#x2F;&#x2F;solarcan.co.uk&#x2F;wp-content&#x2F;uploads&#x2F;2018&#x2F;05&#x2F;solarcan-post-invert-12-expanded-text.jpg" rel="nofollow">https:&#x2F;&#x2F;solarcan.co.uk&#x2F;wp-content&#x2F;uploads&#x2F;2018&#x2F;05&#x2F;solarcan-p...</a>
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Tepix5 个月前
<a href="https:&#x2F;&#x2F;archive.ph&#x2F;usfd5" rel="nofollow">https:&#x2F;&#x2F;archive.ph&#x2F;usfd5</a><p>To avoid HN hug of death on this 1832 users Mastodon instance.<p>Very cool arrangement of those pictures, i was wondering what he has done about the daytime pictures when i read the title.
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crazygringo5 个月前
Incredibly cool. I love this so much, both artistically as well as how it demonstrate the equation of time [1] -- the fact that the changes in sunrise and sunset are not symmetrical.<p>On the other hand, it&#x27;s driving me absolutely crazy that he centers the image at 4:00 rather than midnight. Or maybe that&#x27;s to show the shimmer of sunlight a little after noon on the right hand side?<p>I can&#x27;t figure out why it&#x27;s &quot;bluest&quot; closest to dawn and dusk. I&#x27;m guessing the exposure makes a huge difference, and obviously the night part is way more exposed than the daylight part, or else it would be much darker. Wondering if the camera used automatic exposure, and how much of the brightness of colors in the image are artifacts because of that? Also if he locked the white point hopefully?<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Equation_of_time" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Equation_of_time</a>
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tppiotrowski5 个月前
I generate these type of charts [1] focused on the daylight hours so it was a surprise to see a concave shape instead of a convex one. Awesome way to validate these computer generated charts with captured physical data.<p>[1] <a href="https:&#x2F;&#x2F;shademap.app&#x2F;@52.39941,4.88468,11.49849z,1736006487237t,0b,0p,2m!1735977063143!1736005314203" rel="nofollow">https:&#x2F;&#x2F;shademap.app&#x2F;@52.39941,4.88468,11.49849z,17360064872...</a>
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fiforpg5 个月前
Annnd, this is exactly how humanity figured out astronomy before the telescopes: by taking multi-year observations and keeping detailed records! See Antikythera mechanism, Tycho Brahe, etc. Arguably the entire Greek epistemology was so solid because their astronomy turned out to be an early proving ground for the scientific method.
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drivers995 个月前
I was confused why the night gets so short (looks like 1&#x2F;6 of the time) but I looked it up on a site that shows sunrise and sunset times along with twilight and in the summer it doesn’t even fully get out of twilight. And it seems that there is no correspondingly short day because the sun takes precedence in that the light can bleed over into the night after sunset &#x2F; before sunrise but not vice versa.<p><a href="https:&#x2F;&#x2F;www.timeanddate.com&#x2F;sun&#x2F;netherlands&#x2F;amsterdam" rel="nofollow">https:&#x2F;&#x2F;www.timeanddate.com&#x2F;sun&#x2F;netherlands&#x2F;amsterdam</a>
hinkley5 个月前
My favorite work in this vein is still the guy who did the trigonometry to convert a year+ worth of telemetry from a light level sensor in his back yard to paint a picture of the tree canopy. Each day is a scan line of light and dark patches at a different solar inclination. So everything above the sensor eventually got “painted”.
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th0ma55 个月前
This Python conference presentation from over a decade ago includes an adjustment of such a visualization for DST which I think of often <a href="https:&#x2F;&#x2F;www.slideshare.net&#x2F;slideshow&#x2F;observational-science-with-python-and-a-webcam&#x2F;15993126" rel="nofollow">https:&#x2F;&#x2F;www.slideshare.net&#x2F;slideshow&#x2F;observational-science-w...</a>
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imoreno5 个月前
This is neat, but the amount of data seems overkill just to see the trend in day&#x2F;night length and the keogram is a bit busy. It seems like compressing each day to 1 px tall would result in a clearer representation of that.<p>It&#x27;s neat that you can look at different things, like cloud cover, the moon, stars and anomalies (such as the aurora). But these are convoluted in the raw data. Deconvoluting these to obtain a keogram of just the sun, just the moon, just the anomalies would probably make for some interesting visualizations.
acegopher5 个月前
I did much the same thing (and much more) 10 years ago. I used a RPi as well as a Canon point-and-shot out my window. My pics were 1 per minute.<p>Here is a link to the keogram section (I didn&#x27;t know the term), but watch the whole video, I did a bunch of other art:<p><a href="https:&#x2F;&#x2F;youtu.be&#x2F;Mfo4hVc71Qw?si=3YKojggkTj2xehAB&amp;t=2334" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;Mfo4hVc71Qw?si=3YKojggkTj2xehAB&amp;t=2334</a>
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gregfjohnson5 个月前
This brings to mind something I&#x27;ve wondered about for a while. Sunrise on the shortest day of the year is earlier than sunrise for several days after it.<p>Sunset on these days after the shortest day is of course even later than sunset of the shortest day.<p>On the beautiful image of the OP, you can see that after dawn of December 21, dawn continues to get later over the next few days.<p>In my area, sunrise on 12&#x2F;21&#x2F;2024 was 6:54am, and it will continue to get later until 1&#x2F;8&#x2F;2025, when it is at 6:59am.<p>Length of day on 12&#x2F;21&#x2F;2024 is 9 hours, 54 minutes, and length of day on 1&#x2F;8&#x2F;2025 is 10 hours, 2 minutes.<p>Searching the web, I haven&#x27;t found an explanation for this that &quot;clicks&quot; for me as both intuitive and rigorous. Any thoughts or pointers on this?
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kbutler5 个月前
I was surprised there wasn&#x27;t more of a line of red from sunrise&#x2F;sunset.<p>It&#x27;s probably because the composition algorithm takes a central line through each image (a line through the zenith), so it captures relatively few horizon-adjacent pixels that would highlight the reds of sunrise&#x2F;sunset.
qwertox5 个月前
It took me a bit to understand that it&#x27;s just the red line from the entire dome. It makes me a bit sad that so much information is discarded for these keograms. Isn&#x27;t there a way to &quot;peel&quot; the image in such a way that the entire image ends up being the line? Like spiraling or something like that from the outer &quot;rim&quot; to the center point.<p>Nevertheless, it&#x27;s the first time I&#x27;ve seen this and liked the project a lot. I&#x27;ve seen this from normal images, but not from such a fisheye lens.<p>Really cool project.<p>Edit:<p>Looking at <a href="https:&#x2F;&#x2F;victoriaweather.ca&#x2F;keogram.php?photo=20120810.jpg" rel="nofollow">https:&#x2F;&#x2F;victoriaweather.ca&#x2F;keogram.php?photo=20120810.jpg</a> how can this contain the entire landscape if only the center line is used, which is supposedly always the same line? I mean, the camera isn&#x27;t rotating. Is this just another kind of view generated from the dataset?
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metadat5 个月前
Really cool, this is the first time I&#x27;ve heard of a keogram.<p>I wish there were a corresponding article with a technical write-up covering both the capturing rig and image assembly process.<p>Is there an FFmpeg or imagemagick command, or perhaps a Photoshop script to feed the images into?
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gsich5 个月前
A site with various allsky cameras: <a href="https:&#x2F;&#x2F;www.thomasjacquin.com&#x2F;allsky-map&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.thomasjacquin.com&#x2F;allsky-map&#x2F;</a>
szvsw5 个月前
Highlight related to an analemma: the figure the sun traces if you make a parametric plot of its position in the sky at fixed time T as a function of the day of the year d, ie f_T(d) = (azimuth,elevation).<p><a href="https:&#x2F;&#x2F;solar-center.stanford.edu&#x2F;art&#x2F;analemma.html" rel="nofollow">https:&#x2F;&#x2F;solar-center.stanford.edu&#x2F;art&#x2F;analemma.html</a>
gmiller1234565 个月前
You&#x27;ve got much better weather than we do. Here&#x27;s mine from near Louisville KY (from Aug 2023 to Aug 2024) <a href="https:&#x2F;&#x2F;www.facebook.com&#x2F;groups&#x2F;101640086556073&#x2F;posts&#x2F;7944269998959670&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.facebook.com&#x2F;groups&#x2F;101640086556073&#x2F;posts&#x2F;794426...</a>
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bikamonki5 个月前
So cool that the shape resembles an hourglass!
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diyseguy5 个月前
Why does the sun shrink and disappear just past the halfway point on the keogram?
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j7ake5 个月前
Would love to have these figures as big posters as art decorations in my house
krm015 个月前
Wow this is really beautiful. Is there an algorithm (not api, but available calc method) that can calculate the full year based on a few variables? Like long+lat?
leobg5 个月前
The “stripes” in the keogram look very regular. A few days of clear skies followed by a few days of clouds. Is that what’s happening? Why the regularity?
avipars5 个月前
Were you able to connect IR LEDs to an official Pi NOIR camera and which ones do you recommend?
rollulus5 个月前
Could someone explain to me why the sun-rise&#x2F;set doesn’t seem as sinusoidal as I would naively expect?
justinl335 个月前
the real technical achievement here is maintaining consistent camera sensitivity over 4 years. Most consumer CMOS sensors degrade significantly from UV exposure over that timeframe, which would show up as a gradual darkening in the composite
elintknower5 个月前
Wonder if they&#x27;re going to open source the code they used!
xeckr5 个月前
The dress, anyone?