This is fantastic, and like another commenter mentions, a beautiful continuation of an age old practice: measuring the sky.
Very cool that their hardware keept chugging along for years without hiccup, too.
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.
The results are quite artistic IMO [1], the camera is fire-and-forget and you don't need any chemicals to develop the image. Just photograph/scan the photographic paper and invert the colors.
I'm not affiliated with them, but Solarcan sells ready made single-use pinhole cameras. An almost zero-regret purchase I'd say.
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.
On the other hand, it's driving me absolutely crazy that he centers the image at 4:00 rather than midnight. Or maybe that's to show the shimmer of sunlight a little after noon on the right hand side?
I can't figure out why it's "bluest" closest to dawn and dusk. I'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?
I think the blueness is because clouds at dawn and dusk reflect atmospheric colors more, whereas midday the clouds light up as more of a white from diffusing sunlight. 100% made up theory on my part, but I think it makes sense?
I asked o1 to estimate colors by hour and its reasoning and estimates seem fairly convincing[1], and also show more saturated blues dawn and dusk, though it did not model clouds.
I think because the night sky offers interesting variation that looks nice stitched together. the sunny day, not so much. I will also point out, OCD notwithstanding, that 0hour/12am is an arbitrary time to start the day, and you should really look at the days/nights all strung together in a long continuous strip
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.
This is really neat. I'm curious where the data for the tree shadows comes from though. I was surprised to see that the trees in my yard and my neighbor's yard were all mapped by your service, since I live in a small town in the middle of nowhere. I read the "how it works" FAQ section, which explained that building shadows come from the map services, but it didn't mention trees.
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.
This is something I mention to the younger kids at start parties. Way back then, there was no internet, no devices, no tv, no radio, no movies, and more importantly no easily accessible calendars. You couldn't help but look up at the night sky. There was really nothing else to do, and when the only thing available to know when to plant and harvest was based on the constellations visible at the time. It helps put things into a way that helps them think about it even if they can't quite comprehend not having devices.
I was confused why the night gets so short (looks like 1/6 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 / before sunrise but not vice versa.
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”.
This is neat, but the amount of data seems overkill just to see the trend in day/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.
It'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.
I really enjoyed your faces example! I’ll have to look at the rest of the video soon, but it’s so cool what you can do with a little imagination and ingenuity!
This brings to mind something I've wondered about for a while. Sunrise on the shortest day of the year is earlier than sunrise for several days after it.
Sunset on these days after the shortest day is of course even later than sunset of the shortest day.
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.
In my area, sunrise on 12/21/2024 was 6:54am, and it will continue to get later until 1/8/2025, when it is at 6:59am.
Length of day on 12/21/2024 is 9 hours, 54 minutes, and length of day on 1/8/2025 is 10 hours, 2 minutes.
Searching the web, I haven't found an explanation for this that "clicks" for me as both intuitive and rigorous. Any thoughts or pointers on this?
Here is an approximation that captures the main effect (the 23.5 degree tilt of the earth's rotation axis) and overlooks secondary effects.
Consider the equator. Imagine a circle on the X-Y plane centered at the origin. Angle the circle up 23.5 degrees, rotated around the x axis. The projection of this circle back onto the plane is an ellipse on the X-Y plane, with the vertical axis about 92% of the length of the horizontal axis. Now, consider a series of vectors in the X-Y plane starting on the X axis, with angles in steps of 0.986 degrees. (This is approximately the angle the earth progresses around the sun each day.)
Where each vector hits the unit circle, move the point up or down so that it hits the ellipse. The angle will change a bit for most of the rays. In some cases the angle will be a bit smaller, and in some cases a bit larger. These discrepancies are the variations in time of day of sunrise and sunset over the course of a year on the equator.
The apparent movement of the sun is not influenced solely by the Earth's rotation, but also the instantenuous velocity of revolution and also the fact that Earth's axis is slanted w.r.t. the ecliptic.
It’s partly because we have a standardised 24 hour clock and solar noon (when the sun is highest) is sometimes ahead and sometimes behind GMT noon. The sunrise and sunset times relate to solar noon so they vary accordingly.
See ‘equation of time’ and ‘analemma’ for underlying astronomical explanations, as hinted at by sibling posts.
I was surprised there wasn't more of a line of red from sunrise/sunset.
It'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/sunset.
It took me a bit to understand that it'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't there a way to "peel" the image in such a way that the entire image ends up being the line? Like spiraling or something like that from the outer "rim" to the center point.
Nevertheless, it's the first time I've seen this and liked the project a lot. I've seen this from normal images, but not from such a fisheye lens.
Really cool project.
Edit:
Looking at https://victoriaweather.ca/keogram.php?photo=20120810.jpg 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't rotating. Is this just another kind of view generated from the dataset?
The goal of the keogram is to give a quick overview of sky conditions so you can see if there were clouds, aurora, or other interesting activity. No information is discarded, as the user keeps all of the data, the keogram is just a way of identifying which pictures might have something interesting.
The year long keogram presents even less data, as it's just the centerline of the keogram for each day. So, essentially just the center pixel of each image. Still gives a good overview of what the sky conditions were like throughout the year.
The landscape picture there in your link is a different kind of thing; that one has the column used from each individual photo/frame advance from left to right through the day when constructing the final image, so it still looks like the same static view of the landscape. Of course it's also just a different camera view entirely as well.
The fixed column (and upward view) approach used in the main link is better for showing the movement of the sun/moon/stars.
The capturing rig itself is pretty simple. It's a straightforward project box you can get from amazon. The camera is an astro camera, but you don't need that- a straightforward USB camera from Arducam would work fine (it has to be a wide angle or accept wide angle lenses. Or a raspberry pi High quality camera.
That plugs into a raspberry pi which runs some sort of script or cron job to take a still image. There are CLI tools to do this as well as modify the camera settings (exposure, white balance, etc). There are some holes drilled in the case with a simple plexi dome. Note inside the dome is a ring of resistors which are given electricty through a relay (which is under software control by the pi) to heat up and keep the enclosure clear. I also see a pressure/humidity sensor (likely used to control the relay) and a fan and some desiccant to help keep it dry.
For the software processing you can use anything; I would write a python script to create a large canvas, and then downscale the images and place them at the appropriate location. You could also load the whole dataset into a large tensor and do anything you want with it.
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).
It's easy to forget how far north Europe is! The daytime vs nighttime hours is so much more extreme there. The Netherlands is on the same latitude as Newfoundland in Canada.
I noticed the extreme hour glass shape in his image, but it's even more impressive when compared to yours!
I work with a shorebird expert who has been tracking migrations (Latham snipe whose range extends from Russia/Northern Japan to Southern Australia).
I think an early technique of tracking their migration before gps/chip/batteries were small enough was a primitive light sensor + data logger that would log day/night hours on the bird as it flew from island to island and the light data was enough to roughly estimate lattitute (and often enough to infer a location/date.
The data looked great in this form. It wasn't hourglass but with jagged edges and shifts. You could easily see which months the bird stayed in a single place for several days etc. clever stuff.
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?
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?
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
isoprophlex|1 year ago
Very cool that their hardware keept chugging along for years without hiccup, too.
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.
The results are quite artistic IMO [1], the camera is fire-and-forget and you don't need any chemicals to develop the image. Just photograph/scan the photographic paper and invert the colors.
I'm not affiliated with them, but Solarcan sells ready made single-use pinhole cameras. An almost zero-regret purchase I'd say.
[1] You see the sun move through one year of skies, as seen from my balcony: https://files.rombouts.email/IMG_6500.jpeg
People have made wonderful, mildly spooky pictures with these: https://solarcan.co.uk/wp-content/uploads/2018/05/solarcan-p...
leobg|1 year ago
arduinomancer|1 year ago
Thanks for sharing
Tepix|1 year ago
To avoid HN hug of death on this 1832 users Mastodon instance.
Very cool arrangement of those pictures, i was wondering what he has done about the daytime pictures when i read the title.
changadera|1 year ago
crazygringo|1 year ago
On the other hand, it's driving me absolutely crazy that he centers the image at 4:00 rather than midnight. Or maybe that's to show the shimmer of sunlight a little after noon on the right hand side?
I can't figure out why it's "bluest" closest to dawn and dusk. I'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?
[1] https://en.wikipedia.org/wiki/Equation_of_time
bee_rider|1 year ago
https://fediscience.org/@Birk_lab/113770845539931892
brookst|1 year ago
I asked o1 to estimate colors by hour and its reasoning and estimates seem fairly convincing[1], and also show more saturated blues dawn and dusk, though it did not model clouds.
1. https://chatgpt.com/share/67795fe3-9ac8-8009-9922-153f40c509...
fsckboy|1 year ago
I think because the night sky offers interesting variation that looks nice stitched together. the sunny day, not so much. I will also point out, OCD notwithstanding, that 0hour/12am is an arbitrary time to start the day, and you should really look at the days/nights all strung together in a long continuous strip
tppiotrowski|1 year ago
[1] https://shademap.app/@52.39941,4.88468,11.49849z,17360064872...
nozzlegear|1 year ago
brookst|1 year ago
fiforpg|1 year ago
dylan604|1 year ago
drivers99|1 year ago
https://www.timeanddate.com/sun/netherlands/amsterdam
hinkley|1 year ago
azepoi|1 year ago
th0ma5|1 year ago
th0ma5|1 year ago
imoreno|1 year ago
It'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.
acegopher|1 year ago
Here is a link to the keogram section (I didn't know the term), but watch the whole video, I did a bunch of other art:
https://youtu.be/Mfo4hVc71Qw?si=3YKojggkTj2xehAB&t=2334
kaeland|1 year ago
gregfjohnson|1 year ago
Sunset on these days after the shortest day is of course even later than sunset of the shortest day.
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.
In my area, sunrise on 12/21/2024 was 6:54am, and it will continue to get later until 1/8/2025, when it is at 6:59am.
Length of day on 12/21/2024 is 9 hours, 54 minutes, and length of day on 1/8/2025 is 10 hours, 2 minutes.
Searching the web, I haven't found an explanation for this that "clicks" for me as both intuitive and rigorous. Any thoughts or pointers on this?
gregfjohnson|1 year ago
Here is an approximation that captures the main effect (the 23.5 degree tilt of the earth's rotation axis) and overlooks secondary effects.
Consider the equator. Imagine a circle on the X-Y plane centered at the origin. Angle the circle up 23.5 degrees, rotated around the x axis. The projection of this circle back onto the plane is an ellipse on the X-Y plane, with the vertical axis about 92% of the length of the horizontal axis. Now, consider a series of vectors in the X-Y plane starting on the X axis, with angles in steps of 0.986 degrees. (This is approximately the angle the earth progresses around the sun each day.)
Where each vector hits the unit circle, move the point up or down so that it hits the ellipse. The angle will change a bit for most of the rays. In some cases the angle will be a bit smaller, and in some cases a bit larger. These discrepancies are the variations in time of day of sunrise and sunset over the course of a year on the equator.
incognito124|1 year ago
Study this Wiki article, especially the components part: https://en.wikipedia.org/wiki/Equation_of_time
KineticLensman|1 year ago
See ‘equation of time’ and ‘analemma’ for underlying astronomical explanations, as hinted at by sibling posts.
raimondious|1 year ago
gregfjohnson|1 year ago
kbutler|1 year ago
It'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/sunset.
qwertox|1 year ago
Nevertheless, it's the first time I've seen this and liked the project a lot. I've seen this from normal images, but not from such a fisheye lens.
Really cool project.
Edit:
Looking at https://victoriaweather.ca/keogram.php?photo=20120810.jpg 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't rotating. Is this just another kind of view generated from the dataset?
gmiller123456|1 year ago
The year long keogram presents even less data, as it's just the centerline of the keogram for each day. So, essentially just the center pixel of each image. Still gives a good overview of what the sky conditions were like throughout the year.
zerocrates|1 year ago
The fixed column (and upward view) approach used in the main link is better for showing the movement of the sun/moon/stars.
thanatos519|1 year ago
jstanley|1 year ago
metadat|1 year ago
I wish there were a corresponding article with a technical write-up covering both the capturing rig and image assembly process.
Is there an FFmpeg or imagemagick command, or perhaps a Photoshop script to feed the images into?
dekhn|1 year ago
For the software processing you can use anything; I would write a python script to create a large canvas, and then downscale the images and place them at the appropriate location. You could also load the whole dataset into a large tensor and do anything you want with it.
gsich|1 year ago
szvsw|1 year ago
https://solar-center.stanford.edu/art/analemma.html
gmiller123456|1 year ago
russellbeattie|1 year ago
I noticed the extreme hour glass shape in his image, but it's even more impressive when compared to yours!
bikamonki|1 year ago
mjbrownie|1 year ago
I think an early technique of tracking their migration before gps/chip/batteries were small enough was a primitive light sensor + data logger that would log day/night hours on the bird as it flew from island to island and the light data was enough to roughly estimate lattitute (and often enough to infer a location/date.
The data looked great in this form. It wasn't hourglass but with jagged edges and shifts. You could easily see which months the bird stayed in a single place for several days etc. clever stuff.
diyseguy|1 year ago
icehawk|1 year ago
That's the moon, and it looks like it's increasing cloud cover + dawn causing camera to decrease overall exposure.
j7ake|1 year ago
krm01|1 year ago
leobg|1 year ago
unknown|1 year ago
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avipars|1 year ago
rollulus|1 year ago
justinl33|1 year ago
elintknower|1 year ago
unknown|1 year ago
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xeckr|1 year ago
andix|1 year ago
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unknown|1 year ago
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kyrofa|1 year ago
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Evidlo|1 year ago
galleywest200|1 year ago
Okay, will do.
unknown|1 year ago
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oguz-ismail|1 year ago
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casenmgreen|1 year ago
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unknown|1 year ago
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