SunCalc - a solar azimuth calculator
August 12, 2013 7:35 AM   Subscribe

Suncalc is a nifty online app that lets you input a geolocation and a date, and then uses google maps to graphically display the azimuth for the sunrise, sunset, and current time, for that particular date. Example: the sunset for the May 28 Manhattanhenge.
posted by carter (28 comments total) 41 users marked this as a favorite
Very cool. I was a bit confused until I realized the key has a mistake, the colors for the sunrise and solar noon lines are swapped. The more detailed key has it right.
posted by cosmac at 7:52 AM on August 12, 2013 [1 favorite]

Also MITHenge. (Yes it's a thing.)
posted by madcaptenor at 7:54 AM on August 12, 2013

Neat app. But I had a real freak-out moment when my non-GPS-equipped desktop web browser accurately geo-located my house to within 20 yards. I guess Firefox doesn't just rely on old-school IP geolocation databases, but now also uses WiFi hot-spot databases to get a more accurate fix.
posted by Dimpy at 7:58 AM on August 12, 2013

This is really interesting to zoom into your home and look late June vs. late December.
posted by stbalbach at 7:58 AM on August 12, 2013

This is that rare thing that is much, much better than the description leads you to believe.
posted by DU at 8:02 AM on August 12, 2013 [2 favorites]

This is a lovely tool. See also the 3d version of SunCalc that shows you the sun's transit in a skybox, a very simple planetarium. Built for the 10k apart competition.

Both web apps are by Vladimir Agafonkin, better known as Mourner. He's something of a geohacking genius. His GitHub is full of amazing code. His best known project is Leaflet.js, a lovely Javascript library for making online maps. It's like a lightweight OpenLayers or a free alternative to Google Maps API. It's used all over the place (like OpenStreetMap); I use it all the time myself. The math for SunCalc is on GitHub too.
posted by Nelson at 8:03 AM on August 12, 2013 [2 favorites]

Really reinforces the idea that I should put solar panels on the back roof of my house. Thanks, carter.
posted by Rock Steady at 8:03 AM on August 12, 2013

Sweet. They need to do one for the moon as well.
posted by bondcliff at 8:04 AM on August 12, 2013

Oh this is very cool. I love that I can zoom in far enough that I can see exactly what time the sun will be shining right into my front window in the evening.
posted by capricorn at 8:10 AM on August 12, 2013

Also, I'd like them to integrate this into GPS software, so you can set it to reroute you if the sun is going to be blazing in your face for a portion of your drive.
posted by Rock Steady at 8:12 AM on August 12, 2013 [5 favorites]

Love this! I stumbled on this a few weeks ago when I was planning some photo-shoots. This is extremely cool - thanks for posting.
posted by elwoodwiles at 8:21 AM on August 12, 2013

Man, I've been wondering if something like this exists to the point that I've considered putting together an AskMe to see if anyone could help me figure it out, so this is completely awesome.

It comes from the Manhattanhenge idea - I'd like to see if there's a Universityhenge for Minneapolis/Saint Paul's University Avenue. Looks like September 24th is going to be a cool day.
posted by elmer benson at 8:43 AM on August 12, 2013

Can we please have one for the moon? 'Cause I'm frequently phoning my friends going "OH MY GOD GO OUTSIDE AND LOOK AT THE MOON RIGHT NOW" and about 4/10 times it results in a "I can't find it".
posted by FirstMateKate at 8:45 AM on August 12, 2013

elmer benson - Yes - I found this after getting tired of using azimuth calculators, and then printing out maps and drawing the azimuths on with a protractor ...

I'd like to see if there's a Universityhenge for Minneapolis/Saint Paul's University Avenue

As the avenue runs east/west, you should get the sunrise and sunset in the equinoxes, or around March 21/September 21 every year, although the actual date does vary a little.
posted by carter at 8:50 AM on August 12, 2013 [1 favorite]

Whoa. For years I've been wondering when you might see the sun set behind the Statue of Liberty as the F train passes over the Gowanus Canal. And the answer is TODAY. Meetup?
posted by moonmilk at 9:15 AM on August 12, 2013 [1 favorite]

I use Sun Surveyor (Sun & Moon) on my Android devices - it is very similar to this website and has some other cool tools. It's amazing for photography work.

There's also a free lite version which doesn't do moon tracking.
posted by Fat Elvis at 9:17 AM on August 12, 2013 [1 favorite]

Woah! That is so useful for me. Thanks F. Elvis.
posted by srboisvert at 9:26 AM on August 12, 2013

This is indeed much cooler than I had expected. It is however cloudy out today, so no empirical testing is available.
posted by kiltedtaco at 9:45 AM on August 12, 2013

As the avenue runs east/west, you should get the sunrise and sunset in the equinoxes, or around March 21/September 21 every year, although the actual date does vary a little.

That's only exactly correct if you're on the equator. If you're so ridiculously far north that you only have a few sunrises a year, they're all going to happen quite far north, even on the equinox. If you're somewhere reasonable however, due east/west on the equinox is pretty darn close. Heck the difference is barely noticeable in Tromsø, and that's 69°N.

Hmm. It looks like the times in the UI and in the URLs are in the browser's time zone, which means that link will show slightly different things for different people.
posted by aubilenon at 9:50 AM on August 12, 2013

Yeah, aubilenon, I had just come in to say that. I'm traveling, and it got my current location in Mississippi right but thinks I'm still on Eastern time.

Still and all, very nifty little toy.
posted by solotoro at 11:04 AM on August 12, 2013

I love this, especially the 3D version. But it will be totally useless for the purpose I need it for. I have had some serious arguments (which incredibly enough, I cannot explain due to an NDA) trying to convince people that the sun can never be exactly overhead at noon, unless you're between the Tropic of Cancer and the Tropic of Capricorn, and even then it will only happen once a year, not every day at noon. I will not even get into the arguments over how fast the sun moves across the sky being a factor of the Earth rotating every 24 hours, not 20, not 30, nor any other number. I totally gave up on explaining a sidereal day.
posted by charlie don't surf at 5:11 PM on August 12, 2013

charlie don't surf: It totally illustrates that: The red vector is sunset, the yellow vector is sun rise, the orange vector is where the sun appears at the specified time, and the orange arc is the path that the sun traces on that day. Days/locations on which the sun passes directly overhead, the orange arc goes through the map pin. By playing around with the date, it's not too hard to see that that just never happens outside of the tropics.

Sidereal days are awesome, but just make regular sense. If I were trying to explain, I'd start by pointing out how the moon has days and nights relative to the sun, but the earth never moves across its sky. I guess sidereal months are a nice in between point.

Sidereal years, on the other hand, are just weird and basically arbitrary.
posted by aubilenon at 5:42 PM on August 12, 2013

Right, aubilenon, it totally shows that, IF you are capable of understanding what you're looking at. They aren't. And these are STEM people who should know better. I just cannot dissuade them from believing that the sun is directly overhead at noon. I have tried everything, I even tried to explain the Analemma. They look at me like I'm talking about astrology. So I tried explaining it with astrology. That didn't work either. I showed them computer generated images of the Earth viewed from the Sun angle at solar noon at the equator on the equinox, vs. the angle at the Tropic of Cancer at the Solstice. They do not understand what I am talking about. I might as well be talking about the Hollow Earth theory.

I find it absolutely mindboggling that the entire history of math and science basically evolved from prehistoric men looking at the motions of the stars and planets and trying to figure it out, and yet some modern scientists cannot comprehend the most basic concepts of the Earth's rotation and orbit around the Sun.
posted by charlie don't surf at 6:01 PM on August 12, 2013

Here's my attempt to document gowanuslibertyhenge - from a moving train with a crappy cell phone camera. It almost worked! I can't tell if the sun is too high or too low (already set but illuminating the clouds). I may try again tomorow.
posted by moonmilk at 7:13 PM on August 12, 2013

Synchronicity or something. This _almost_ solves a somewhat simple thought experiment I've been thinking of, but I need the 3d one to allow me to set the location on earth and for it to plot the suns path over a whole year (probably weekly or every few days).

My question is "Does the suns track in the sky ever overlap itself in the visible sky?"

I think the answer is no (with the caveat that it touches at sunrise/sunset) near the equator and yes near the poles. I've reasonably convinced myself of the second part (maybe), but am not sure about the first part. The 3d tool could probably show this if I could figure out how to put in arbitrary latitudes.
posted by jclarkin at 3:40 PM on August 13, 2013

My question is "Does the suns track in the sky ever overlap itself in the visible sky?"

Yes it does. The Sun takes the same path through the sky at any two dates exactly one solar year apart, so during those two days it will be in exactly the same spot in the sky (geocentrically).

Also the Sun will be in the exact same position in the sky twice a year, which means the paths will cross at that time. See The Analemma. I am not sure if it happens more often than twice a year. Just eyeballing the Analemma, I think the paths will cross frequently during the period between the Vernal and Autumnal equinoxes (geocentrically, from the Northern Hemisphere). I will have to do the math and check.
posted by charlie don't surf at 4:41 PM on August 13, 2013

Well, I wasn't considering pure overlaps where the sun takes the same path a year apart (approximately, as the exact path won't be repeated perfectly ever, but will be pretty close every 4 years), but paths that intersect without taking the exact same path, ie places where it crosses over itself. But I'd really need to see the plots to be sure.

The analemma is a result of the earth's elliptical orbit, I think. Otherwise the analemma would be a straight line rather than a figure 8.

It's annoying but I may have to find or calculate the data and plot it to convince myself of an answer.
posted by jclarkin at 2:25 PM on August 14, 2013

And clearly I'm terrible at visualizing things in my head. The analemma would still be a figure 8 is the Earth's orbit were circular. It just wouldn't be asymmetric.
posted by jclarkin at 2:39 PM on August 14, 2013

« Older "Some things...can only happen once."   |   Stop-and-frisk on trial Newer »

This thread has been archived and is closed to new comments