Light trespass

In previous "view from your app" images we have only had a few examples of light trespass: when light illuminates something it is not meant to illuminate.

My colleague Catalin-Daniel Galatanu sent me an excellent example of light trespass from Iași, Romania. In the photo below, you can see a residential building that is brightly illuminated by the spill light from church facade lighting:

Light trespass by Catalin-Daniel Galatanu is licensed under
a Creative Commons Attribution 4.0 International License.

Catalin used his images to calculate the luminance of the facades, and got the following result:

Light trespass luminance by Catalin-Daniel Galatanu is licensed under
a Creative Commons Attribution 4.0 International License.

The lit areas have a luminance of 2-4 cd/m². To calculate the illuminance on the windows it would be necessary to know the albedo of the building, but with a rough guess of 0.7 that would imply around 15 lux. I think it would be pretty unpleasant to have such a bright light shining into either your bedroom or living room! Catalin points out that in addition to the light in the room, the people living here have lost not only the view of the stars from their window, but they wouldn't be able to enjoy their view over the city at night, due to the unpleasant glare.

It's important to stress that there's absolutely no reason that it has to be this way. With more carefully directed lighting, the church could be illuminated with limited or no spill light. Furthermore, it's not necessary to shine so much light on a facade for it to have the impression of being illuminated. I hope to soon be able to share a great example of how churches can be more effectively lit (paper in review).

Sometimes lamps make it hard to see

When you ask the question "why do we have outdoor lighting" the reason most people come up with first is for safety". But it often happens that lamps actually make vision worse than it would be if it wasn't there, as we've seen on the blog before. Lighting can be especially tricky near staircases.

I'm currently in Montsec, Spain, for the 4th LoNNe Intercomparison Campaign. We are staying in a wonderful hotel in a region that is brightly lit with stars. On the days that the hotel has kept the lamps off for us, this staircase has been easy to climb with adapted eyes under starlight:

But on the first night we were here, it looked like this in the night:

The light flashed through the stairs, and made it very difficult to see. The culprit was this old-timey style lamp mounted near a doorway below:

If the lamp was better shielded so that it didn't shine sideways (and upwards), the guests at the hotel would have a safer and easier trip up to their rooms at night.



The three photos above by Christopher Kyba are licensed under a Creative Commons Attribution 4.0 International License.

Model of exponential growth in skyglow at one location

Andrej Mohar produced a video modeling skyglow changes from 1950-2040 at Matajur mountain on the border of Slovenia and Italy:

The simulation is based on a calibrated all-sky image taken at the site, with an estimate of 5% annual growth in skyglow (which is a pretty reasonable assumption for the later half of the 20th century). But there's no reason that skyglow must continue growing at such a rate! If we get smart about how, where, and when we light, we could recover the starry skies that many of us remember from our childhood.

The night sky over Westhavelland, Germany

A few weeks ago I was in Sternenpark Westhavelland (International Dark-Sky Reserve Westhavelland) to try to measure the degree to which individual streetlights affect the night sky in a pristine area. The lamps are part of a biological and ecological field experiment of the Verlust der Nacht (Loss of the Night) project, funded by the German Ministry of Education and Research (BMBF).

Together with a colleague, we walked different distances from the lamps and then remotely the lights them off and on. In addition to measurements with a continuous logger, I took a few all-sky images. This one is from the middle of the field when the lights were off:

Verlust der Nacht field at night by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

You can download the full resolution version here. The sky is blue because it is lit by lunar twilight. The glow at the right (East) is a combination of the moon and the city of Berlin. The glow at top left (southeast) is the nearby town of Rathenow.

The next photo shows the view a few hundred meters from the field when the lights are turned on (the field is the bright glow at right):

Verlust der Nacht field lit at night by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Finally, this animation shows how the whole environment near the field changes as the lights turn on:

Verlust der Nacht field turning on by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

I think the lighting up of the nearby tree and grass is the most dramatic - just think of what a complete difference this is for the insects and birds that live there! Here's a higher resolution version.

UPDATE Nov 23, 2015: We have published a paper describing the field site and a few of the first experimental results. You can read about it for free at the journal Sustainability.