Sun Position Calculator | Hacker News Reader

Sun Position Calculator

drajmarsh.bitbucket.io

170 pointssanbor36 comments

Archived version: https://web.archive.org/web/20260111135022/https://drajmarsh...

Awesome, thanks for the backup link.

Amazing visualizer!

Some friends flew eastwards from New York to Singapore on a direct flight (it's one of the longest flights). I wondered what their experience of sunrises and sunsets were (they departed 10PM), I've noted down the times but haven't plotted it...

Later this year I'm flying from Europe to the West Coast of Canada, and it seems I'll be in daylight for the entirity of the flight (departing 2PM local, landing 4PM local after a 10 hour flight).

Edit: well, FR24 has a handy flight tracking that includes the daylight progression: https://www.flightradar24.com/data/flights/sq23#3de5a306

So they flew 18 hours and experienced a full daylight cycle, arriving just before the second sunrise...

I flew from central US to western asia (via moscow) and it was an interesting experience for the reasons you mentioned. I think I left early Saturday morning local time and arrived Sunday evening local time. I saw a sunrise, sunset, sunrise, sunset in 18 hours of travel time.

I wonder what the physical toll on a man exprriencing three consecutive solar days?

On a long haul flight, the crew usually tells everyone to shut the window blinds, because many people want to sleep, so you don't get to see the sun.

I had interesting flights in end of june from St. Petersburg to Novosibirsk. It departed at around 23:00, and you saw sunset and still a dawn. As the plane flew mostly at latitude of 60°, the dawn in the north was always there, and 1.5 hours later, the sun rose. The plane arrives after 3h30m of flight at ~7:00 local time, in summer solistice the sun is already high enough.

Neat. Similar to https://www.suncalc.org, which also lets you zoom to the neighborhood level. Very useful to figure out when/where sunlight will hit your house.

There's also https://shademap.app/ for that, also useful (with 3D buildings!). Used it before buying my condo and it was spot-on.

This is probably the most clear explanation of the seasons and the changing altitude of the Sun that I have seen. This would be perfect for school lessons or popularizing science.

Here's a fascinating video of what the sun does at 90S: https://vimeo.com/208466944

I would say this is the prettiest interface I've seen for explaining seasons, analemma, solstice, ... to someone or experimenting myself.

Thanks for the find!

Cool demo!

I notice that the stars don't seem to be rendered correctly. If you zoom out, you can see the sun's position relative to the stars. As you scroll the date slider through the course of a year, the sun should make a complete 360-degree revolution around the ecliptic. Or, when the camera view is locked to the sun, the stars should appear to revolve relative to the sun.

Instead, the sun appears motionless against the stars, regardless of the time of year. (If the demo used actual star positions, I would be able to point to how the sun was in the wrong constellation for a given date. But the starfield is randomly generated, so you have to actually observe the sun in motion to see the bug.)

Tangentially related — on my website I track coffees I’ve enjoyed and show their origin on an interactive globe.

https://farrant.me/coffees/

The tilt of the globe on that page changes throughout the year to match The Earth’s tilt when viewed from from The Sun. The initial rotation of Earth is correct for the time of day too. This means that, when you load the page, you see The Earth as The Sun currently sees it.

I’m not sure anyone has ever noticed, and I’m sure my calculation isn’t perfect, but I enjoy watching it change over the course of the year.

This is really, really well done. I’m very impressed by all the features implemented here and I wish I could look over the source. I wonder how it is done.

Relatedly, has anyone seen tooling or approaches to calculate shadows behind particular hills and mountains, depending on the season and time of day? The sunset calculation for Boulder Colorado is quite inaccurate as we are in the foothills with mountains to the west. I've been pondering how to calculate this precisely.

You would basically want to calculate the solar altitude angle (or, equivalently the zenith angle): https://en.wikipedia.org/wiki/Solar_zenith_angle

Given the mountains, the sun would appear to set when it descends below some altitude angle. Given the equation in the wikipedia article you'd then just solve for the hour angle. (You'd then have to use your latitude to convert the local solar time to Mountain Standard Time.)

Of course, if the mountains are not flat then the altitude is then a function of the azimuth...

Perhaps a rough look-up table for (say) each 10 degrees of azimuth around the observing point that gives the altitude to solve for? Finally a couple of iterations to find what azimuth the Sun will be nearer the actual setting time, perhaps taking the 'flat horizon' setting time as a starting value?

https://stjarnhimlen.se/comp/riset.html#2

I live in a street that faces roughly north/south so we get an early dusk at this time of year in the front room. I feel a spreadsheet coming on...

https://shademap.app/@40.02101,-105.3587,10.26063z,176851848...

Don't immediately see a way to get the actual estimated sunset out of it, but you can fiddle around manually

> The resource from “https://drajmarsh.bitbucket.io/earthsun.min.js?vpd-10161” was blocked due to MIME type (“text/plain”) mismatch (X-Content-Type-Options: nosniff)

Outstanding design and implementation! Really great for visualizing the sun, earth, and seasonal relationships!

One minor nit I notice is the Latitude slider on the right seems reversed from what I'd expect. I would expect Slide UP to move North and increasing positive latitude numbers, and DOWN for South/negative, but this implements the opposite. It seems this may be to match the Longitude negative numbers at the top, but that convention seems a lot less necessary, i.e., either would work for longitude and +=UP/-=DOWN for latitude seems like it is more important to match with the physical and mental models?

Thanks for the cool tool, I'll be using it a lot for garden planning and solar panel install (and just cool to look at)!

I recommend activating "Show Illuminating Sun Beam" under "Explanatory tools" by clicking the graduation cap icon in the top right corner.

This is a cool visualization. I wonder if it uses the excellent solpos.c library from NREL as the core engine?

https://www.nrel.gov/grid/solar-resource/solpos

I've been wanting to make a little circadian rhythm graphic based on the sun, would love to have a graphic like this to support it. If Andrew Marsh is listening, would love to create something to extend what I have (Preview at sun-taupe.vercel.app)

This is really cool! The clock on your page reminded me too of some sites that show a "real solar" time based on your location where solar noon corresponds to 12:00 PM.

Right. My theories and hunches to support this that got jumbled up due to AI slop, were that syncing to the sun over a “9-5” or “8 hours of sleep” would improve and align our health better than any scientific system would. The sun is the enabler of science in a weird way.

Like there’s culture that have a siesta at solar noon and it’s a time to rest: that means the sun’s noon time not our arbitrary time or 12pm every single day. Lunch annd exercise could also follow for productivity gains to happen at particular times of day.

The first 'observatory' was a stick placed vertically in the ground such that it's shadow traced the angular relationship of the sun & earth

And in one year of observations they noticed that the point of the stick followed an 8 shaped track on the ground. I wonder what they thought about it.

I attempted to build a naive sundial last year and I was surprised when I saw the sun moving east to west (or vice-versa, can't remember) at the same hour. It's very noticeable week over week.

https://en.wikipedia.org/wiki/Analemma

If only we had a perfectly circular orbit and no axial tilt!

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This is great for photographers planning golden hour shoots. The neighborhood-level zoom is particularly useful.

*golden shower?

amazing work...

is it possible to add moon to it as well. that would make it more intuitive.. looking at the night moon its possible to find where the sun is but not possible to imagine the respective location of earth with respect to moon and sun.

This is incredibly cool!

Love it. Needs a moon.

OSINT tooling.

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