Wednesday, July 9, 2014

How to find pictures of cities at night

Update December 16, 2014: NASA has changed their website around, breaking nearly all of my links to their pages. I will update this post sometime over the Christmas break.

Astronauts have taken over a million photographs of Earth from the International Space Station. Many of them have been taken at night, like this one of Berlin:

Berlin at Night from the ISS, original image ISS035-E-17210 available here.

NASA has made all of the images freely available through its "Gateway to Astronaut Photography of the Earth". But when you've got a haystack of 1.2M photos and you just want to find the original of the one Chris Hadfield took of Calgary at Night, you could use some help to find what you're looking for.

A group of ISS photo enthusiasts and light pollution researchers have solved your problem by putting together an Atlas of nighttime images of the Earth. This post is a short note to help you use a feature of the Atlas that's not necessarily very obvious from the main page.

When you go to the main page, scroll down to "Gallery of cities at night". Here you can scroll and zoom over the Earth to find a city (like Calgary). When you click on the dot, it will pop up some information about the photo, as well as a thumbnail:

The thumbnail has a link to the photo at the NASA gateway - but if you click on it you'll notice that it's not the one that Commander Hadfield tweeted! The problem is that multiple photos of Calgary have been taken.

While the Atlas website is super for finding cities that have been imaged, it's not what you want to use if you're looking for all photos of a given city. To do that, you want to click below where it says "Original at"

When you click there, you will get to a google spreadsheet that looks like this:

Now click on "Table of data" near the top left, type the city you're looking for in the box at the top left, and then click "Find":

Now you can see more detailed information about the photos, including thumbnails and links to the NASA site if you scroll way over to the right. The photo that Chris Hadfield took is the top one on the list, and now you can go to the NASA site and get the link to the full resolution photograph of Calgary at night.

The last step is to scroll down on the NASA page to the two "view" buttons. Click on the bottom one:

and voila, here is your full resolution image:

Calgary at Night from the ISS, ISS034-E-44268

The images from the NASA site are all free to use, provided you acknowledge the photo source (there is a recommended citation at the bottom of the page). To make it easier for other people to find the photo in the future, be sure to always include the image designator that starts ISSxxx.

If you use the Atlas to find a photo and then publish the photo somewhere, then please also cite this paper: Alejandro Sánchez de Miguel, et al., Atlas of astronaut photos of Earth at night, Astronomy & Geophysics, Vol. 55 no4. August 2014 (in press).

Going forward

The best part about the Atlas website is that it includes three citizen science projects to ensure that future photos are cataloged, and to find other older images "hidden in the dark of the database".

Dark Skies of ISS allows citizens to sort images between different types: Images of cities, images of stars, and other images. It requires no previous knowledge, and is only available online. It is the simplest of the three projects.

Night Cities aims to allow citizens to apply their lay knowledge of local and international geography. The project shows paired images of cities with maps. Project volunteers identify points in the night images and match them to positions on the maps. With this help we can generate light maps of cities.

Lost at Night is the stiffest challenge for citizens with good geographical knowledge of a region. Their goal is to identify which city is in an image without any identification. The position of the cities in this case is only known to within about 500 km.

Note: If this is your first-ever visit to the blog, welcome! The blog is about a citizen science app called "Loss of the Night". We need your help to understand how changes in street lighting technology are changing the night sky. You can read our introduction to the blog here, and instructions on how to use the app here.

There's lots more to see, including:

You can see bring up our entire photo series via this link. Thanks for visiting!  

Tuesday, July 1, 2014

A travel to dark sky places in the USA

Astronomer and natural night sky campaigner Andreas Hänel recently returned from the USA where he traveled 7600 km in order to see the sky at a number of pristine and polluted sites in the American Southwest.

Andreas wrote up his observations, so you can read about his trip (and see dozens of great photos) here (pdf).  When he got back to Germany, he took this great photo in the Black Forest:

Galactic center viewed from the Black Forest by Andreas Hänel
is licensed under a Creative Commons Attribution 4.0 International License.

The view may not be as good as in the parks in the USA, but at least it's good to know that such views still exist in some places in the South of Germany. Maybe 30 years from now, better lighting will help clear the skies further towards the horizon.