Thursday, February 23, 2017

A step by step guide to using the Loss of the Night app on Android (v2.1.7)

This is a step by step guide to using the Loss of the Night app for Android (v2.1.7). If anything is unclear, let me know in the comments and I will revise the instructions.
Instructions for iOS
Infos auf Deutsch


Requirements:


Android phone running at least Android 2.1, but preferably Android 4 or higher.
The phone must have a compass and GPS.
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, turn off the app and leave the area immediately!

Installing the app:


To install the app, do a search in the play store for "Loss of the Night". Alternatively, type this address in your browser: http://tinyurl.com/vdn-app

or go to the page by scanning this QR code

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" at the bottom right hand of your screen.

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, you will be asked to indicate your approximate age (use the up and down arrows to change), and you can click the buttons 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. Click "save" when you have entered your data.

Making an observation


After you save your data, you'll come to the main menu. To make an observation, click "start observing stars". 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 takes longer than that, try using an app like "GPS Status" to check if your phone's GPS is working. Some phones have a problem that prevents the app from getting your position from GPS. In this case, try putting your phone in airplane mode and starting the app again. We are working to understand and fix the problem, but this provides a temporary fix for some Android devices.

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 arm until you see a star with a flashing 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), "barely visible" (you can see it while looking at it directly, but just barely), or "visible only with averted vision" (you can see the star only when you don't look directly at it).

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. On some Android devices, quitting the app and then starting a star search again results in a smoother response. 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 four options for why you can't see the star. Choose the option that is most appropriate:



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



You can view all data collected by participants via the My Sky at Night website. Click the blue bar at upper right to select which years and data sources you would like to observe. An overview of the My Sky at Night website is available here.

The app also stores the results of your observations directly 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. (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.

Friday, February 10, 2017

Excellent LED streetlamps

This December I visited my family in the town of Wetaskiwin, Alberta, Canada. The first evening that I drove into town I immediately noticed that the city had switched from Sodium lamps to LED, and I was very pleasantly surprised to see that the LEDs they chose shine the light very carefully. To see what I mean, take a look at the photo below:

Good streetlamps are invisible by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.


You almost can't see the streetlights at all, because they shine light on the street, rather than into your eyes. On most lit streets around the world, you can see the lamps from kilometers away, because they shine a portion of their light directly into drivers eyes. These photos from Wetaskiwin show how unnecessary that glare is.

That being said, the lamps aren't entirely glare free, particularly for pedestrians (see below). However, in terms of (white) LED streetlamps deployed in an urban setting, these are the best I have yet seen.

Close-up glare by Christopher Kyba is licensed under
a Creative Commons Attribution 4.0 International License.

When you have a good light distribution, then you can light the streets and sidewalks, and avoid shining light into peoples bedroom or living room windows. Take a look at the photo below. One house is lit with Christmas lights, but did you notice the one to the left? The street and sidewalk for that house are lit, but the facade of the house is not.

Orion over LEDs by Christopher Kyba is licensed under a Creative Commons Attribution 4.0 International License.


Camera photos don't accurately represent what our eyes really see (which is why I often show photos using two different exposures). I didn't do that (or HDR) in this case, because I hadn't planned on taking photos and wasn't dressed for the cold. But you can take my word on it: as a pedestrian, you have no problem to see the house on the left, the camera doesn't show it because the exposure was set to highlight the lit snow.

Thanks to Rod Mc Connell and Noel Smith, I was able to get some information about the lamps themselves. They are the "RoadFocus" series manufactured by Philips lighting.

The only negative side with the current lamps is that they are 4000 Kelvin, which produces considerably more skyglow than a lamp with a lower color temperature (warmer, less blue light). But I hear the city is planning on switching to 3000K in the future, and is also thinking about reducing the wattage so that the lights don't shine overly brightly.

So hats off to the city of Wetaskiwin for choosing driver friendly low-glare lights!

Here is a copy of the original photo, in case you'd prefer it without the text.


Good streetlamps are invisible by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Monday, January 30, 2017

I use my sun visor at night...

A loss of the night app user from Trier, Germany, recently passed me a few photos to share with you. They show the results of a recent lighting "upgrade" in his area. The problem with the new white LEDs is that they are extremely glaring. The glare is in fact so bad, that he needs to drive with the sun visor down! Glaring lighting makes it harder for drivers to see pedestrians, but there are efficient LED streetlamps for sale that aren't as glaring. So if your city installs something like this, be sure to complain! Even better, let the city council know you care about quality lighting before they make a change!

This work is licensed under a
Creative Commons Attribution 4.0 International License.

This work is licensed under a
Creative Commons Attribution 4.0 International License.

This work is licensed under a
Creative Commons Attribution 4.0 International License.

This work is licensed under a
Creative Commons Attribution 4.0 International License.

This work is licensed under a
Creative Commons Attribution 4.0 International License.

He also sent me a photo of the skyglow on the horizon towards the Big Dipper:

This work is licensed under a
Creative Commons Attribution 4.0 International License.


(The title of the blog post comes from a song by Canadian singer Cory Hart: Sunglasses at Night. If you've never heard it, take a listen and see if it reminds you of another famous song)

Thursday, January 12, 2017

Converting World Atlas floating point values into sky brightness predictions

Over the past several years, I was involved in the team that published the "The new world atlas of artificial night sky brightness" last summer. My main role in the project was in calibrating the map based on sky brightness observations. The two main sources of observations were the all-sky brightness surveys of the US National Parks Service Natural Sounds and Night Skies Division and observations with hand-held or vehicle mounted Sky Quality Meters (SQMs). In the end, we chose to do the main calibration with the SQM dataset, because thanks to the participation of citizen scientists, it covered locations on all 6 inhabited continents, including many more urban locations than were otherwise available. The NPS surveys, some additional telescopic data, and data from permanently mounted SQMs were then used to verify the result from the SQMs.

Now that the Atlas is published, many researchers are interested in using the map to understand their area. For most people, and also for many researchers, the colorized version of the map that we've made freely available is sufficient. For example, if you're looking for a good place to go stargazing, you'll do fine with the colored map. You can either view the Atlas with from within your web browser, or you can  download a set of tiles for Google Earth.

The rest of this post is technical, and will only interest a small subset of blog readers.

Some researchers will want to use the floating point dataset for further analyses. The data is currently not openly available, but can be requested via a form from this page. The form sends an email to Fabio Falchi, who will follow up with you regarding terms of use*. (Publicly funded researchers from the USA and Germany intending to use the data for non-commercial research purposes should be allowed access without fees. Other national research organizations and anyone interested in using the data or imagery for commercial purposes may be asked to license their use.)

The floating point data are stored in a single GeoTIFF file covering nearly the entire world's extent (arctic latitudes excluded). The map reports simulated artificial zenith luminance in mcd/m2. If you want to use the data to estimate how bright a real sky is, you need to add in the natural portion manually. Natural light at night is quite variable, mainly due to the position of the Milky Way and the amount of airglow that is present.

When we calibrated the World Atlas, Dan Duriscoe from the US NPS provided me with estimates of the natural sky brightness for the specific date and time the observations were taken at each of the tens of thousands of locations worldwide. These observations were taken from 2007-2015, with the largest number of observations taken in 2013 and 2012. Over this time period, the predictions for the natural sky brightness ranged from 21.01 to 22.11 mag/arcsec2. The most typical value was 21.65 mag/arcsec2 (or about 0.236 mcd/m2). The average value changed over the years (due to changing solar activity), from faintest values of 21.88 mag/arcsec2 in 2007 to brightest values of 21.58 mag/arcsec2 in 2014.

Once you choose a natural sky brightness**, you should add that value (in mcd/m2) to the artificial sky brightness from the Atlas. Let's call this value "X". To convert this value into a prediction of what an SQM would see, use this equation:

SQM_pred = -2.5 log10(X/ (10.8 x 107))

I'd like to thank to Salvador Bará for sending me a question that prompted me to write this blog post.

* For researchers using the data in publications, please note that the data DOI is separate from the World Atlas publication. If you write a manuscript using the data, you should separately site both the World Atlas publication and the data DOI.

** Note that in the model we also included an additional free parameter "S", which is a linear scaling factor for the natural sky component. We put it in to account for the fact that the SQM band does not match the V band. The best fit for this value was 1.15, meaning that the average natural sky brightness was increased from 21.65 mag/arcsec2 (0.236 mcd/m2) to 21.50 mag_SQM/arcsec2 (0.271 mcd/m2).




Monday, November 14, 2016

Four super activities for tonight's "Supermoon"

Tonight is the night of the "supermoon", meaning the moon happens to be close to it's "perigee" (the closest it gets to the Earth) at the same time as it is full. As it happens, tonight's supermoon is an especially good match between moment of fullness and perigee: the last time the full moon was this close to Earth was in 1948, and the next time it will be this close is in 2034.

When the moon is closer, it appears ever-so-slightly larger than normal. This makes some people roll their eyes at all the attention, but I think anything that gets people out to experience the night should be celebrated! With that in mind, here are four things you can do to celebrate tonight's moon (the first 3 are great for kids):

1) Watch the moonrise

When the moon is near the horizon, an optical illusion makes it look bigger than usual. This makes every moonrise special, but the experience is most exciting when the moon is big and full. One fun activity, especially for kids, is to bend over and look at the moon upside down through your legs. For many people, this destroys the illusion, so you can switch back and forth between having a big and small moon.

You can look up the moonrise time at your location here. For observers at high Northern latitudes where night is already falling, the moon will appear quite red, because the blue light is scattered by the atmosphere.

2) See how well you can see with only ~0.2 lux.

Once the moon has risen high in the sky a few hours later in the evening, go out into an area that's as free as possible from artificial light. A big (unlit) park or sports field will work in a city, and an open field works best in the country, but a back yard will do in a pinch. You'll probably find that you can see better than you can on a typical urban street, even though lit patches under streetlights are usually 100-500 times brighter than full moonlight. The reason for this is that the moon lights the landscape uniformly, and most importantly without glare. A recent paper argues that even older pedestrians need only 1 lux to avoid stumbling, and this experience shows to what extent we could reduce energy use and light pollution if we improved urban lighting to make it more uniform.

3) Test whether you can see color and read text under full moonlight

Before you head out the the park, grab a colorful magazine and take it with you. Many people can read text and see colors in full moonlight, but a lot of people incorrectly believe that the moon isn't bright enough. Who in your family can read the easiest? Can you tell what all colors are, or just some of them? Speaking of colors, use something to block out the moon and look at the sky around it. Many people experience the sky as shining blue near the moon.

4) Take moonlit landscape photos

If you have a camera with a programmable shutter speed, you can take absolutely wild photos by moonlight. All you need is a tripod or stable surface to rest your camera on (here's a moon landscape photography tutorial in case you want to get really serious). Once the moon is high up in the sky, take a photo of the landscape, and you'll end up with a fully lit scene, but with stars shining in the blue sky!

An example of one of my favorite moonlit photos is below (although this was far from full moon, and the exposure was kept short because the moon was in the photo, so the sky doesn't appear blue):

Moonrise over Nationalpark Müritz by Alejandro Sánchez de Miguel is licensed
under the Creative Commons Attribution 3.0 Unported License.

If it's cloudy or raining where you are, you could try for two other phenomena. One of the hardest things there is to photograph is a moonbow: a rainbow lit by moonlight:

Moonbow, Kula, Hawaii by Arne-kaiser is licensed
under the Creative Commons Attribution-Share Alike 4.0 International license.

Finally, if it's overcast where you are, I'm still waiting for someone to answer my challenge of taking a landscape photo on an overcast night in an area without significant light pollution. Maybe tonight will be the night!

Thursday, September 8, 2016

Second community App experiment!

It's high time for another community experiment using the Loss of the Night app!

Last year we examined how stars come out during twilight, which is also useful for understanding the different times at which stars come out for people. This time, we're going to try seeing how much variation there is in an individual observation due to the random set of stars selected by the app.

To take part, you should make an app observation with 8 stars (quit once you've reached 8 stars). Then, start the app again, and do a second 8 star observation. To make sure that we don't see changes due to city lights going off, both observations should be completed within a single 30 minute period.

Both times you run the app it will probably start with the same first and second stars, but the rest of the stars are likely to be different. Since you are the same observer looking at the same sky, your data will help us understand how much of the variation in observations is due to the design of the app itself, rather than differences in sky brightness.

You can do this on as many evenings as you want to from September 22 until about October 6. I'll present the results in an app newsletter email and here on the blog towards the end of year.

Friday, May 27, 2016

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.