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

astrodon.social

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

#22

Post by szvsw »

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).

https://solar-center.stanford.edu/art/analemma.html

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

#23

Post by tppiotrowski »

brookst wrote: post #20
tppiotrowski wrote: post #17

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. [1] https://shademap.app/@52.39941,4.88468,11.49849z,17360064872...

Pretty! But daylight savings time messes with the aesthetic.

True. Argentina doesn't have DST and I just realized living in the northern hemisphere made me miss the fact that the sunlight hours chart is concave in the south

https://shademap.app/@-50.35203,-70.98027,4.13034z,173600823...

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

#24

Post by hu3 »

Evidlo wrote: post #6
kyrofa wrote: post #2

[flagged]

The modal at the bottom says rate limit exceeded. Don't know why it says 404 instead of 429

There's no modal at the bottom on mobile for me.

So just 404.

And why would someone flag that users message for stating a fact.

People will click the link, see 404, and leave confused. That flagged message is useful.

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

#25

Post by drivers99 »

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.

https://www.timeanddate.com/sun/netherlands/amsterdam

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

#26

Post by brookst »

tppiotrowski wrote: post #23
brookst wrote: post #20

Earlier quoted context omitted.

Pretty! But daylight savings time messes with the aesthetic.

True. Argentina doesn't have DST and I just realized living in the northern hemisphere made me miss the fact that the sunlight hours chart is concave in the south https://shademap.app/@-50.35203,-70.98027,4.13034z,173600823...

Yep. Could flip either one by starting July 1.

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

#28

Post by metadat »

Really cool, this is the first time I've heard of a keogram.

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?

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

#30

Post by bee_rider »

crazygringo wrote: post #16

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"…

One of the commenters noticed this as well, the author says it is something automatic in the exposure.

https://fediscience.org/@Birk_lab/113770845539931892

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