Great observation from Portugal

I wanted to share a great observation made a few months ago by a Loss of the Night project participant from Portugal:

As you can see, there is a very clear separation (white line) between the stars that were visible (yellow, orange, and brown) and those that were not (black). You can also see how thanks to the observer examining so many stars, you can have a lot of confidence in the result, and can even measure how consistent the observer's result is. When you first start using the app, you might not have results as consistent as this, but with a bit of practice it becomes easier and easier to cover a lot of stars quickly.

This also demonstrates why the app is a better method for estimating limiting magnitude in bright places than star chart based methods like Globe at Night. In this case, the naked eye limiting magnitude was around 3.9 ± 0.1. The star charts of Globe at Night only allow you to choose between integer limiting magnitudes, which in this case would be "about 4". In addition, with Globe at Night we can't be sure how careful a participant is, and we found that compared to skyglow models, the standard deviation of Globe at Night observations is about 1.2 magnitudes.

While the app can provide more accurate data, I want to stress that it's not a replacement for Globe at Night! The app doesn't include stars with limiting magnitudes above about 5.2, so in areas with little light pollution, Globe at Night is a better method. In addition, the Globe at Night time series goes back over 10 years, and there is therefore a lot of value in continuing to contribute to it. In my opinion, it's the best system we have for tracking global changes in skyglow. So please consider contributing to both projects!

If you make an observation with the app, you can easily see a similar plot for your own results. Just head to My Sky at Night, zoom in to the area where you made your observation, and click on it to bring up this chart.

Skyglow surveys with an SQM and the Loss of the Night app

I was just looking through the Loss of the Night app data, and noticed that a project participant used the app and an SQM to do a skyglow survey of the island of Öland, Sweden:

Öland skyglow survey is licensed under a
Creative Commons Attribution 4.0 International License.
Link to the interactive map at www.myskyatnight.com.

I reached out to Jörgen Tannerstedt, in order to get the story behind the map. Here's what he told me:

The story behind the measurements is that we last year started a project called "Dark sky Öland" in the local astronomical society on the Island of Öland, Grönhögens Astronomiska Förening (GAF). We are a rather small astronomical society, with fewer than 30 members, but we like our island and the darkness that we've got, and we want to protect it for the future and make others aware of it. There are also some plans/thoughts of applying to IDA and try to make some part of the island a dark sky park or reserve. The southern part of Öland is a world heritage site, and perhaps one could try to make that to a light protected area as well.

"Night over the lake" is copyright Jörgen Tannerstedt.
Used with permission.

As a first step in this project we bought a SQM-LU meter to start measuring the sky brightness all over the island. I guess I´m the most active member in our society, so I got the meter in my hands and have brought it with me most of the time when I´m out shooting. I take mostly astroscape images from the island, some of them can be seen here.

I recently got myself a telescope, and had it just set up before we lost the dark nights here up in the north. So now we just want the summer to end and get the darkness back :P August 10th is the first night with astronomical darkness again after the summer break for the island.

"Stargazing" is copyright Jörgen Tannerstedt.
Used with permission.

So far I have measured over a hundred different locations on the island, several locations multiple times and I will continue doing this during the autumn. There are still several good locations left, and I also want to measure in and close to villages to see how much influence they have, and how much light is spread to the nearby surrounding.

It´s rather recent that I discovered the Loss of the Night app, and it has made things so much easier for documenting the measurements. I really like the ease of use, and that the observations are automatically GPS tagged.

Our measurements will be used to evaluate how good and dark the sky is, and serve as a "before" value to see if it gets better or worse in the future. For example, the area near the bridge to the mainland is under heavy construction, and a lot of new houses are being built with road and street lights etc.

The measurements are also going to be used in a guidebook that another member, Lars Magnusson, is working on. In the guidebook, we will include a lot of good locations for astronomers that want to come to the island and experience our dark skies. We will also include information about the different locations, availability, public toilets, photos etc. Hopefully will we have a first version ready this autumn

When shooting from the southern cape of the island, the camera can easily pick up light from cities the other side of the sea, like Gdansk/Gdynia area in Poland. For example, in this picture the light pollution out to the right under the central parts of the Milky Way are from Gdansk/Gdynia, about 250 km away.

If anyone would like to come and visit the island we have the astronomical darkness back again august 10th, and then later in the beginning of september with the new moon, we have our yearly star party "Sagittarius". It's a rater small party with some spontaneous lectures during the daytime and most often a geological excursion and then stargazing all night :D It's always nice to meet others with the same interest. During summertime, there are a lot of tourists here, from Germany, the Netherlands, and Belgium. We've even got a hotel here that is named "Drei Jahreszeiten*". The winter is not that fun, and pretty windy here, so I understand they skipped that season :D But so far I haven't heard anything about any astrotourists.

* "Three seasons"

My hat goes off to Jörgen and the other members of GAF for documenting, sharing, and especially working to preserve your natural starry skies on the island of Öland! Hopefully your book will lead to a few extra astrotourists to fill up the Drei Jahreszeiten hotel!


While it's nowhere near as organized as what GAF is doing, I have taken advantage of my trips to the state of Mecklenburg-Vorpommern in Germany with some similar goals in mind. I also hope this area will someday be home to one or more recognized International Dark Sky Places, where the communities have recognized the value of the night sky as a natural resource, and agreed to work together to protect it. Here's my map:

Skyglow survey MVP is licensed under a
Creative Commons Attribution 4.0 International License.
Link to the interactive map at www.myskyatnight.com.

If you have an SQM, this method of surveying is a wonderful way to contribute to environmental monitoring of Earth's night! The data are shared with everyone around the world, and they contribute to a permanent archive of the skyglow conditions at the site. If you are planning on founding an International Dark Sky Park or Reserve, this allows you to document the conditions at your site transparently, and future visitors will be able to verify your results and contribute to monitoring changes in the sky condition.

Please note that the best way to do an SQM measurement is to average the result of 4 measurements with your body oriented in the four different compass directions. This is the recommendation from the Loss of the Night Network, and we have found that it considerably reduces the size of the uncertainty compared to taking just a single measurement. Here is the full text of the recommendation from the LoNNe report:

Recommendation #1: When making observations with a handheld SQM-L, you should average the result of four observations, rotating your body after each observation to a different compass direction. If the SQM-L is being affected by stray light, this may minimize or reveal the effect. If the four observations are not self-consistent (maximum range about 0.2 magSQM/arcsec2), then it is probably not a good location, and the data should not be recorded. This technique has been suggested by Andreas Hänel in the past, and we advise all handheld SQM-L users to adopt it.

First community experiment!

During the coming week (until August 14), we are running the first in a series of Loss of the Night app community experiments. This month we're asking people to make multiple observations as the stars come out during twilight. Since many observers live in places without much light pollution, twilight offers a way to do an apples-to-apples comparison.

The more people that take part, the more likely that we'll have a result that's statistically interesting. So if you have a clear sky sometime in the next week, try making an 8-star observation after the first star is out but before it's gotten all the way dark. Try to do the measurements quickly, so that the sky doesn't darken too much while you are observing.

I will present the results of the experiment at the webinars in September, but there will probably be a sneak preview for everyone on our mailing list.

Using the Loss of the Night app while traveling

In the last week, two people have asked me about using the Loss of the Night app while on vacation. The short answer is yes, you don't have to do anything special, the app will work when you are traveling and don't have access to a data network, and the data will be sent to us when you return home.

The slightly longer answer is that there are two minor things to keep in mind:

1) Getting a GPS fix will likely take much longer (in the worst case up to 10 minutes), because the app can't download the GPS satellite positions and has to wait for the satellites to broadcast their "ephemeris data". Please be patient, it should eventually work. You can debug whether things are working using a GPS app like "GPS Visualizer".

2) Your observation data will not be sent to us until the next time your phone connects to the Internet (e.g. via WiFi). You can check the status of the measurement in "User data > My measurements". The status will either be "waiting" or "successfully sent". Once you are connected to the Internet, the app should send the measurements by itself automatically.

In the past, there were two minor bugs that affected using the app during international travel. I think they've both been fixed, but these are hard bugs to test, because to properly test them you need to fly halfway around the world!

The first bug affected the position of the stars. The first time you used it overseas the app would display the stars over your home. The workaround was to simply run the app twice, the second time the stars would be displayed correctly.

The second affected sending the data when you connected to WiFi. On some occasions, it didn't happen automatically. A workaround is to do another observation when you have a WiFi or network data connection - you can even run the app in the daytime in "demo mode", and after you finish the observation the app will send both the new and old data.

Finally, we really appreciate it when you take data in additional locations! The more places that are sampled, the more accurately we'll be able to measure the global rate of change in skyglow.

The Loss of the Night app is two years old!

April 22 is the second anniversary of the Loss of the Night app! Since that time, tens of thousands of people have installed the app on their phone, and thousands of those people have used the app to make at least one observation of the night sky.

Here are some statistics from the first two years (for data up to April 18):

20,170 individual observations have been submitted from 9,825 unique devices from around the world (see map below). This number includes "demo mode" cases when people are just testing the app, and observations with clouds and sunlight or moonlight. Most devices have only ever observed once, but over 100 people have submitted ten or more observations.

App observations up to April 18. Black points are all observations,
red points are observations with no twilight, moonlight, or clouds
and at least 7 stars observed.

In the first few months, only about 10% of the submitted observations were suitable for analysis (no clouds, moonlight, twilight, and at least seven stars observed). This fraction has steadily increased over time, and is now close to 30% of the observations submitted. The number of good observations per month is also climbing, but slowly. The more participants we have, the quicker we'll be able to measure the average change in sky brightness worldwide, so tell your friends about the app!

Citizen scientists have searched for a total of 30,323 stars (under nighttime conditions). The star most commonly searched for so far is Capella (694 times), followed by Vega (593x) and Altair (554x). Since the new version was released, many of you are now submitting more than the minimum seven stars. We really appreciate it, because observing more stars leads to a more precise result.

The mean time to observe a star is 34 seconds, but the most frequently occurring time needed to make a decision is 11-15 seconds. Your data help us understand which are the "best" stars for us to ask you to look for. I hope that we will do one last update to the app's "star selection algorithm" in the next year or two, so the more stars you observe, the more you'll improve the app.

In addition to the naked eye observations which are the main purpose of the app, citizen scientists have also used the app to submitt 239 observations taken with Sky Quality Meters under nighttime conditions. Of these, 188 of which were taken with with no cloud cover.

Thank you to everyone who has taken part in this project to measure how Earth's night sky is changing. It wouldn't be possible without you! The next moon-free observing period starts around May 7. If you don't yet have the app, here are the links for downloading it for Android and iOS.

Minor bug report

Users at high latitudes (like Germany) may have noticed today that the app crashed after it acquired a GPS signal. The bug was caused by an expectation that the "next good time" to observe should be within 30 days, but during the summer at high latitudes the twilight extends past the time we thought people would be interested in observing.

The bug has been fixed, and in the next few hours the update should be available in the Play and App stores. We didn't notice the bug in testing, because our testing took place after the midsummer twilight was over last year.

Observers in Germany that are willing to stay up past midnight are able to observe from about May 7-18. If you live at a lower latitude, the bug probably didn't affect your phone.

Future upgrades to the app

How can we improve the app?

A bit more than a year ago I asked for your help in how we could improve the app. I updated the list as suggestions came in through comments, email, and in-person discussion, and with the release last fall a lot of the improvements made it into the app.

Now that the new version has been out for a few months, I want to start a new list for a future third - and ideally final - release. We have no source of funds at the moment, but I think it's valuable to keep track of what needs changing/fixing. If you have more suggestions, please let me know in the comments.

Things to change/improve in a future version of the app

Star search

• Further improve star selection based on app data (preferentially use easier stars)
• Make more use of "pointing stars"
• Allow search to start with Venus or Jupiter
• Allow the user to change the sensor settings (speed and/or damping) to make the display more comfortable
• When screen is frozen, allow navigation by sliding finger 
• Allow the user to adjust the number of stars displayed on the screen to match a given skyglow level? (a bit dangerous, as this could potentially cause biased observations)
• Shaking the phone unlocks the locked circle (goes back to arrow) 
• Try to work out that the user is standing on a balcony, and don't suggest stars in that direction 

Usability

• Figure out what causes the occasional crash on startup
• Better way to deal with very bright locations
• Strategies for classifying areas with NELM>5
• Interface to allow advanced users to submit what their estimate of the limiting magnitude is
• New "constellation mode". Highlights a single constellation, and the user has to click on a star to declare it visible (turns from dot to star) and click a second time to declare it invisible (turns from star to empty circle or x), click third time for "just at visible limit"
•  Or extend this mode to cover several hundred stars over the whole sky, and the observer can just pick which ones she wants to label?
• Arrange "my measurements" by date
• Manual way to calibrate the compass to remove azimuth error 
• Add a compass-free option in "settings" menu for places with weird magnetic fields
• Investigate behavior of auto brightness on Android (does it turn to full on app startup?)

Community

• Have the database in the background: users can log in see their observations - where they were taken, how they relate to those of others, see the observations of others, tools to examine how it is changing over time, see the accuracy of the data they gathered themselves
• Graphical web display of your like I have shown on the blog in the past
• Option to share your observation via facebook and twitter
• Badges - you've observed 7 stars, you've repeated an observation at the same location ~1 year later, you've done 10 observations, 5 times in a single city, 5 locations, etc...
• Guide users to locations that we particularly need measurements (e.g. repeat measurements from previous years).
• Incentivize good data: Have a friendly competition where the best quality and quantity is rewarded (with a visit to the closest telescope and a personal lecture from an astronomer). Reward observations in particularly important locations

Extra features

• A "talking" tutorial that tells you how to find the stars, asks you to turn in different directions, etc.
• Video tutorial
• Find a way to calibrate the compass within the app (on Android, iOS already has this)
• Port to WindowsPhone and Blackberry
• Allow observing below 45 degrees and making maps of the stellar visibility on the full sky dome
• Check the clock using GPS and warn the user if their phone's clock is off by more than 2 minutes (and then exit app). Prevents records having a false time
• Allow option of displaying user's location on a map to make sure it is correct
• Check whether the phone has a compass, and don't allow install if there is no compass
• Ability to export your observations (e.g. to an email)

Technical

• Change behavior of star search with "averted vision" decision (technical)  
• Start looking for GPS location on app start up, verify again before star search
• Especially for SQM report, GPS should run in the background while typing value
• Reduce the size/thickness of the circle during the star search on Android
• Better messaging in "Not dark enough" menu during high latitude summer 
• Allow users to add SQM serial number

Now it's your turn. What other changes should we make to the app?

Data not yet appearing on GLOBE at Night maps

We haven't yet updated the scripts that process Loss of the Night app data for the new data format that is produced by the new version of the app. Because of this, your observations might not appear on the GLOBE at Night map. You can check if your data was sent on the "User Data" page under "My Measurements". If it says "successfully sent", then we should have your data.

I will try to remember to post when we have new scripts up and running to generate the points for the map. Sorry for the inconvenience!

An example of user data with the new version of the app

I've been browsing the incoming Loss of the Night app data, and I wanted to share the details of a recently submitted observation.

One of the things that we changed in the new version of the Loss of the Night app (iOS, Android) was to give users more options to describe what stars look like. The original app had three options: visible, not visible, and unsure. In the new version*, we now ask users to distinguish whether the star is "clearly" or "barely" visible, and added a new option, "visible only with averted vision".

If you've used the app outside, you've probably noticed that sometimes you can't see a star when you look directly at it, but when you look off to the side it appears. This is because the very center of your eye is packed with color sensing cones for vision in daytime, rather than the rods we use to see at night. The cones aren't sensitive enough to see the star, but if you look just off to the side, your eye has enough rods to let you see it.

The plot below shows the observations that project contributor Matt Sidor took using the app on the outscirts of Davis, California a few nights ago. The filled in blue circles are stars that are clearly visible, the black stars are stars that were barely visible, filled in red circles were visible only with averted vision, and empty red circles were stars that were invisible.

Matt did a fantastic job! With 14 stars, he had almost perfect separation between the stars that he could see directly and the stars that he couldn't. The new classifications give us more information than was available in the old version, and should lead to more accurate estimations of the sky brightness.

The other thing the image shows is how the app now focuses much more carefully on stars close to the limiting magnitude. Compare the stars Matt was asked to see with older data from the original app version below:

The older version of the app was much less aggressive about testing stars near the limiting magnitude. We expect that by staying closer to the limit, user observations will be more accurate. When an observer makes a mistake (it happens!), the range over which the app tests grows in response. When you finish your observation, the app will let you know how accurate your measurement was. If you use the app over time, you can see if your accuracy improves as you get more practice!

* I'd like to acknowledge this recent paper by Andrew Crumey as the inspiration for us to move from 3 possible classifications to 5. In case you don't have access, a preprint is also available.

New version of the Loss of the Night app is released!

The updated version of the Loss of the Night app is now available for iOS and Android!

The app lets citizen scientists like you measure how bright the night sky is, by seeing which stars you are able to see. The more faint stars you can see, the more natural your sky is. Your results are then shared with the GLOBE at Night project, and will be used to track how the night sky is changing in response to widespread adoption of LED lights.

What's in the new version?

• Improved feedback: We fit your data and tell you the estimated naked eye limiting magnitude, approximately how many stars are in your sky, and how consistent your observations were:

• Smoother behavior: Phones that had problems with an unstable star field should now be fixed.
• More customization: You can change font sizes and switch the screen brightness between a city/country mode. Pinch zooming will replace the zoom buttons.
• Better night mode: Removal of gray backgrounds and replacing orange with red in many places.
• Improved measurement technique: new options to tell us if the star is clearly or barely visible, or if you can only see it with averted vision
• Better set of stars used: So the app is quicker and easier to use, and more accurate
• Expanded language support: To Czech, Hebrew, Slovak, and Turkish
• News about our project: Links to these blog posts on the news page
• Calculation of next possible observing time: If the moon is up, the app will figure out when the next good (evening) observing time is for your location, and let you put it in your calendar
• Feedback button: So you can tell us what we should do next! 
• Faster GPS convergence

Thanks to everyone who gave us feedback on how to improve the app, to the translators, and to everyone who has used the app and provided us with data. This new version couldn't exist without you!

Now, we need your help once again to spread word about the app, because the project will only be a success if there are thousands of people taking data worldwide. So please post news about it on social media, tell your friends about the app, and give it a good rating in the app and play stores to help make it more visible!

If you'd like some more information, you can read our press release. Step-by-step guides for using the app are available for iOS and Android.

A step by step guide to using the Loss of the Night app for iOS

This is a step by step guide to using the Loss of the Night app for iOS (v1.0.4). If anything is unclear, let me know in the comments and I will revise the instructions.
Instructions for Android
Infos auf Deutsch 

Requirements:

iPhone (some iPads can also be used)
A location with a light polluted sky.
A friend to accompany you while you are doing observations.
The ability to see at both near and far distances without removing glasses.
Your phone case must not have a magnetic clasp.

Before you start:

The Loss of the Night app is meant to be used outside at night. For safety's sake, inspect the area where you plan to do your observation during the day, and make sure that it has level ground where you can move around safety.

People using mobile phones are less aware of their surroundings, so you should never use the app alone outdoors at night! Always take a friend to watch out for potential hazards while you are using the app. These could include tripping hazards, vehicles, dangerous weather, and crime. If for some reason it's not safe to do an observation, put down your phone and leave the area immediately!

Installing the app:

To install the app, visit this link. If it doesn't work for some reason, just do a search in the app store for "Loss of the Night".

Running the app:

When you first open the app it will display the privacy policies and terms and conditions. To go further, you will need to read the conditions and then click "Accept Privacy Policy", then "Start Application".

When you click "accept" you are brought to a screen with information about light pollution. Click "next" to go on.

Next comes a screen titled "USE". We would appreciate it if you would register and tell us something about your vision and your observing experience. Click "Register Now" or just "Continue as a guest".

If you choose to register, tell us your approximate age by clicking on the word "Age" and then scrolling to the correct age range. Click elsewhere on the screen to select the age. Next, click to tell us whether you wear glasses, and how much stargazing experience you have. We also ask you to provide a username and your email. If you provide your email, we will send you a thank you email within about a month of your observation. In extremely rare cases we contact a user if we have questions about their data. When you have finished entering your information, click the ⧁ button to go to the main menu.

Making an observation

To start an observation from the main menu, click "start observing stars".  The screen will show you an indication asking you to tip your phone into landscape mode. It should go away when you tip the phone. (If it does not, your phone may be set to lock the screen in portrait mode. You will have to turn this setting off to use the app.) At this point, the app will only work properly if you're outside, as it needs to get a GPS signal. This can sometimes take up to a few minutes.

If it is still twilight or if the moon is in the sky, the app will give you a message that it's not "dark enough". The moon prevents measurements from being made for about two weeks at a time, so if this is the case, the app allows you to add a note to your calendar when the next observing period at your location starts. (Click "Measure anyway" if you'd like to test out the app.)

(At this point, in locations with a lot of magnetic material or electric cables around, your phone may give you a warning that your compass has a problem. You can try to calibrate it by moving your phone in a figure 8, or turning it around all three axes. It this doesn't work, then there is either a problem with your location or your phone's compass. You can opt to measure anyway, but the stars displayed on the phone will likely be shifted compared to the ones in the sky.)

Next, you are asked to input the current weather conditions. Click the relevant symbol (or symbols), and then "Continue".

Star search

The app will now try to direct you to one of the brightest stars in the sky. Turn your body in a circle and watch how the arrow changes direction. Tilt your arm down so that your app is pointed toward the ground, and it will show you the stars that are under the Earth. Tilt your arm up to the sky, and it should show you the stars that are currently in the sky. It is very important that while looking at the stars in the sky you keep the phone's screen oriented perpendicular to your body!

Now search for the star the app is asking you to look for. Turn your body until the arrow points straight up, and then raise your arms until you see a star with a crosshair on it. When you find the star, the circle will expand to fill most of the screen and three buttons will appear at the bottom of the screen.

Your job is to decide whether the star the app pointed you to is visible to your naked eye or not. If you can see the star, then click "Star is visible" on the bottom right. The app will then ask if it's "clearly visible" (very obvious and easy to see) or "barely visible" (you can see it while looking at it directly, but just barely).

If you cannot see the very first star, there may be something wrong with your phone. The app always starts with one of the very brightest stars in the sky, which should be visible even inside of large cities. The most likely problem is that your compass is not working properly. If your phone is in a carrying case that has a magnetic clasp, you will need to take the phone out of its case and then recalibrate the compass (quit the app, and then start it again).

If the stars appear to be bouncing around a lot, you may be in a location with strong electromagnetic fields (e.g. near overhead or buried power lines). It's best to try to use the app in a grassy area, like a park. Finally, it's possible that the compass or GPS from your phone is not working properly, and if this is the case the app will not work on your phone.

Continuing your observation

Each time you find a star, the app will ask you if it's visible or not. If you can't see the star for some reason, click on "Not visible or unsure". You will then be brought to a menu that gives you five options for why you can't see the star. Choose the option that is most appropriate:

If you can see the star only when you don't look directly at it, or if is only visible some of the time, then choose "Visible only with averted vision". If you're not sure which star we're asking for, or if for some reason you find it too hard to tell whether the star is there or not, choose "I'm not sure if it's there or not".

Once you have made a decision on a total of 8 stars, the app will pop up a message that says "8 stars reached". You will have the option to quit, "Register" (if you haven't done so already), or "3 more stars". We would really appreciate it when you observe a few additional stars, because observing more stars improves the accuracy of your measurement.

If you click "3 more stars" the app will ask you again when you reach 11, 14, and 17 stars. After that, if you want to continue, it won't interrupt you anymore, and you can click the "back" button whenever you are ready to end your observation. When you end your observation, the data is automatically sent to a server hosted by the GLOBE at Night project if your phone has an Internet connection. If you have a data plan, this should happen immediately, otherwise, it will be transferred the next time you have a WiFi connection.

When you finish your measurement, the app will let you know how faint the faintest visible star in your sky is (naked eye limiting magnitude), and approximately how many stars are visible in your sky. For reference, in places without light pollution, it's possible to see many thousands of stars. The app will also let you know how consistent your measurements were. The more you use the app, the better you will get at making accurate, consistent observations!

Accessing your data

The app stores the results of your observations on your phone. In the main menu, click on "User data" and then "My measurements". A screen will come up showing the dates that you did observations, and the results. If you click on an observation, then the app will show you the names and magnitudes of the stars that you looked for, and what your decision was (stars with smaller magnitudes are brighter.)

Personal settings

The "User data" menu allows you to change some of the app settings. You can toggle the display of star and constellation names, and choose whether some screens display on start up. You can also increase the size of stars and fonts (this might help if you are farsighted). If you find that the screen is too bright during your star observations, click "Make screen darker" and see if it helps.

Additional information:

As the year goes on, different stars appear in the night sky over your head. If you enjoy using the app, feel free to use it as often as you like!

The app contains a lot of information about light pollution that you might find interesting. You can access this information by clicking on "Project information" in the main menu.

You can also switch between "Day mode" and "Night mode" in the main menu. Please use the Night mode when making observations, because it is designed to have less of an effect on your night vision.

If you have a Sky Quality Meter, you can submit data taken with the device as well. From the main menu, click "Submit data from SQM" and then use the scroll wheels to enter the SQM value.

More information about the Loss of the Night app project is available on our blog.

If you'd like to read a paper that demonstrates the scientific value of citizen observations of naked eye star visibility, you can access it for free here.

The app is available in 15 languages, and automatically uses the language that your device is set to.

Thank you!

Thank you for taking part in this project! Your data will help us understand how the brightness of the night sky is changing around the world. Because we are interested in understanding long-term changes, the most valuable data are observations taken at the same place year after year.

A step by step guide to using the Loss of the Night app on Android

This is an old version of the instructions for using the Loss of the Night app for Android. New instructions for version 2.1.7 are available here.

Loss of the Night app expanding to 15 languages!

The updated version of the Loss of the Night app is going to come out very soon. In addition to lots of new features, we've added support for Czech, Hebrew, Slovak, and Turkish.

We would like to recognize our volunteer translators for their considerable donation of time to this project:



Arabic: Amr Al-Omari
Catalan: Salvador Ribas
Chinese: Yongguang Zhang
Czech - Milada Moudrá, Michal Bareš
French: Olivier Domingue, Johanne Roby, Martin Aubé, and Romain Clément
German: Annette Krop-Benesch
Hebrew - Roni Segoly
Italian: Andrea Giacomelli
Japanese: Nobuaki Ochi
Polish: Ania Wisniewska
Romanian: Catalin Daniel Galatanu
Slovak - Jaroslav Merc, Peter Begeni, Pavol Rapavý
Spanish: Salvador Ribas
Turkish - Nail Köker

Thanks to all of you for helping make this a truly international project!

If you are interested in helping us expand the app to include your language, please send me an email.

GLOBE at Night observing period begins tonight

Once again the moon has gotten out of the way in the evening, and it's possible to observe skyglow via GLOBE at Night, the Dark Sky Meter app, or the Loss of the Night app. This early evening moon free period runs until October 23.