 so let's start all right who doesn't know it the presets are in August so you would like to watch what are they called the things you wish on and but you can't see them always and Jan Zodermann is looking at this he's an engineer and astronomer and he works at the inspectors at their observatory in I forgot all right thanks a lot for the introduction about spectroscopy we heard something earlier so you inspect the light of stars and things like exoplanets those are of course very advanced subjects we're from flying a space telescopes in space you can see but also from telescopes on earth and there are a lot of different factors here which make this possible such as the persuades you can even identify exoplanets and we have this association amateur observatory in the other to the whole time in somewhere between Düsseldorf and Wuppertal and you can imagine that is an area that is very densely populated and not the ideal place for astronomy so we formed a working group there and here are the names of that working group of the members and everything I'm presenting now is a collaborative work of this working group and it also happened in a time without stars this idea and our idea was that we would look into light pollution for it because we need for one clear sky but also a clean sky to make good astronomical observations and you should already noticed over the decades that the sky at night is no longer really dark and what kind of influence that has on people and animals and the environment I don't want to talk about that but we task ourselves to use our devices our instruments to inspect this light pollution a bit more closely because it disturbs the visual observations and it disturbs even more the astrophotography and spectroscopy itself so as I said this is the observatory in the Scharnher a bit to the right of this marker in the middle of the map it's a bit east of Düsseldorf which is down there the bright point that is noise and above is Duisburg so along the Rhine you can see it's a very densely populated area which results in this brightness at night we can see their own eyes and this map you can see find on the internet under this light pollution map info address and you can check there for your own position current data in this map it's refreshed every couple years the data is behind this and then you can look where around you there it might be a bit more dark at night or if you really want to see the pursuits on already bright summer night sky where you might be able to drive a bit to have success in observing it but a map like this reflects the absolute brightness of the sky in a clear night and there are specific measuring instruments in astronomy we use the magnitude as brightness and this map was created through measurements from different positions what we've done now we're not directly interested in the absolute brightness but we wanted to know what kind of light is that what kind of colors are there disturbing our recordings and we took out our spectroscopes for this and measured the intensity across the whole color spectrum and it looks a bit like this you can see those gray bars up there those are several recordings into different directions which were put next to each other where we can see these white spectral lines so as mentioned earlier the Fraunhofer lines and the presentation like nude there they have dark absorption lines but here in front of dark background we have these bright emission lines they're called and these images generated with an electronic camera are evaluated by magnitude and then you can see these curves down there in the lower part of the picture although those were also shown next to each other as above so those aren't the absolute brightnesses but you can see in parallel one curve has peaks another curve doesn't have those peaks are there weaker but what this is that's the question now so for observing the sky we use these telescopes and this is a mirror telescope and next to it on the lower left there is this white box and then in the back you can see the body of digital XLR I think it's called and this is the digital spectroscope where that contains the optical elements with which we can split the light that we see through the telescope optics and for this measurement we didn't use a telescope like this but we wanted as we'll see later to be mobile with this so we connected the spectral apparatus to a zoom objective and with this zoom lens we made this the sky measurements but in the spectroscope itself the most important element is a so-called reflection grid I think and that's a mirror with 200 lines per millimeter and then that looks like a CD if you hold it into the light you the light is split into its spectral colors and then this signal is captured and evaluated and we are interested in light contamination And for this, in last spring, we took cloudy nights and took our zoom lens with a special aperture point into the sky in different directions and then we measured these emission peaks and then there was this and then at the bottom of the scale we can see these lines that go up vertically this is an extra calibration lamp where we can see neon light from a neon light bulb which we added because those lines we know exactly where they are and with those lines we can get scale and then know the actual wavelengths of the other lines so in spectroscopy you always work by putting the blue corner on the left and then on the right the red end of the visible spectrum so on the left we have the short wavelengths here shown in angstrom and then on the right in red going over into infrared we see the long wavelengths of the lights and what can really disturb such a recording is not just on the cloudy sky what we recorded there but there can actually be these distances in a clear observation night as well and this is an example from Harald from our group who did a large area but weak object so that's a North America Nebula which is a cloud of gas and dust which is which shines by itself and then in the curve below it the red one you can see the light pollution at the same location in a cloudy sky and in the upper sky in the upper curve we can see several peaks or emission lines that are not in the lower one and those are the emission lines that come from this gas nebula and with suitable programs you can subtract these curves from each other mathematically and then you get the pure lines of the emission nebula of this gas usually hydrogen and oxygen nitrogen and then you get those all right the light pollution that we have seen with these recording in the different directions we wanted to identify this where does this come from and so we took out our spectral apparatus with camera and the zoom lens and we walked through or drove through the city and record some examples of different lamps so from the street lights that we saw there and this first one is the classic yellow light that you can see in the street lights and also in industrial areas often in industrial halls so that's the sodium vapor lamp I think and a spectrum on the right you can see the individual emission lines because in this lamp sodium is vaporized and then it shines in its fairly pure yellow spectrum and here's a different example we found the modern street lights with LEDs where there are pure white LED lamps as well as ones that are a bit tinted especially where there is a crosswalks and you can see a big difference to the image earlier this LED lamp because it's supposed to shine white it is composed out of a big area in the visual spectrum also has a peak in the red area but at the end you have there all the different colors and it's a big it's almost a normal distribution of these wavelengths so that you can already imagine this is difficult to filter out and in between we have the generation of street lamps with these fluorescent lights which might contain quicksilver which is a metal that's vaporized in this lamp and then has a single sharp emission line and we have very different kinds of emission from these very different kinds of methods of illumination and these individuals spectra from the different light sources we took and made an image of this whole contaminated of this cloudy sky and associated them and you can definitely see find them in there so you can see the peak of the fluorescent lights or also the sodium-sodium area with the closely clustered lines and you can see all this in the light that gets reflected from the cloudy sky and which we then also get in a seemingly clear dark night and it's still in there and the less there are still lines here which we have not observed so there are still other light sources that could be for instance vehicles so Xenon or those halogen lamps or in this love itself there are streets and in the old city their parks and sidewalks which are really lit with gas lamps so gas is actually being burned there and those lamps are protected monuments and those might also be in here but we have not identified this closer we wanted to see what is going on there and what kind of lights are disturbing there observing the sky visually or with photographs and the conclusion is that it has gotten worse due to this LED light because this sodium light can be filtered out you can take a filter that's designed for this which just filters out a small area of the spectrum and then you have the information of the rest of the spectrum to the right and left of it you have that in your image but the disturbing light of a single sodium lamp or a single quick server one can be filtered out real good filter when taking a photo but with this LED lamp that's more difficult because we have seen it's almost a normal distribution across the whole spectrum the emission lines and you can't really filter that out you would filter out all the other information as well so and destroy this information so you wouldn't have anything left in the measurement so one important realization is and we communicated this to the people from the Robin works I think as well if you take this LED lights which saves energy then you should also go so far that you make it very targeted lighting technology in the city and avoid as much as possible having light leak into the sky and also maybe control the lights so that if nothing is there no traffic then maybe you can turn them off as well there are also smart systems for this of course so this is our conclusion we can do a lot with filters with LED lamps we can't do anything we can only call upon the responsible places to do responsible lighting of only where you really need it and ensure that there's as little a leak light as possible and this whole subject that I described now we have created two posters as well one in German one in English was presented at the last Congress in Lübeck and they're at Faudius Astro so that's the spectroscopy conference you can download them as well and distribute them wherever you want if anyone's interested and the poster is available for free use yeah thanks a lot for paying attention a slightly complicated subject but very concrete one so in the summary we're not only looking at very exotic things we can also use our devices for very