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<p>Just got a note from our local astronomy club, McGill University has a research project going on about light pollution and dark skies. If you want to play with your camera to shoot the big dipper constellation and contribute to the data base, the link is <a href="http://www.hep.physics.mcgill.ca/ASTRO/darkskies.php">http://www.hep.physics.mcgill.ca/ASTRO/darkskies.php</a> They're looking for shots all around the world. Now, if I could just get some clear skies! Bad enough that low pressure system ruined my view of the Lyrid meteor shower over the weekend, now it's dumped a bit of snow on us and just won't shove off.</p>
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<p>I was unsuccessful in digging up an article I have on light pollution and dark skies. </p>

<p>The article referred to nitrate radicals (NO3) as natures way of cleansing the atmosphere of airborne particulates (smog) caused by man's activity, but this cleansing only occurs at night as sunlight inhibits the process. It is the airborne particulates that reduces seeing conditions as light is scattered by its presence, so what we call light pollution is really air pollution which will diminish seeing even in the absence of light. </p>

<p>Most cities now use high-pressure sodium or metal halide lights pointing downward to reduce its interference with nitrate radicals cleaning air pollution, and from an astronomy observer's viewpoint, physical light shields and filters can be a very effective way to image the sky but if you want to see millions of stars with the naked eye, air pollution is our enemy. </p>

<p>So this raises interesting questions on what McGill is attempting to accomplish through its gathering of photographs. </p>

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During WWII, "dimouts" were enforced within 50 miles of the Atlantic coast so German subs could not target freighters against the skyglow from shore. The milky way was always visible on cloudless nights and northern lights were also spectacular when the conditions were right. (I'm referring to eastern Massachusetts.) Now you have to be far from the East Coast to see either of these. Dark skies would be great.
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<p>"<em>It looks like they're gathering data on the brightness of the night sky in different locations."</em></p>


<p>Yes, but what is the data they hope to extract and how useful would it be?</p>

<p>They ask for:</p>


<li>10 second exposure</li>

<li>ISO 800</li>


<li>Hi-resolution JPEG (if possible)</li>

<li>Avoid nights with a bright moon. For example, wait for the moon to set.</li>


<p>There is no mention of "no post-processing", and an un-tweaked shot typically taken in a suburban setting might be an orangy mess populated with white dots. I suppose they can infer light pollution from it and correlate the result with location, but how would that be any more efficient than looking at a satellite image of any given geographic location on the planet at night?</p>

<p>There is also no mention of looking out for cloud cover high in the atmosphere, and seeing conditions will also marginally improve as the night progresses. There are simply too many variables they need to account for.</p>

<p>The picture posted below might resemble what they have to work with - taken from this thread:<br /> <a href="../photo/2617978&size=lg">http://www.photo.net/photo/2617978&size=lg</a></p>

<p><img src="../general-comments/attachment/1764747/_dsc2288_s.jpg" alt="" width="510" height="339" /></p>

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I asked, and got a response: "The purpose of this project is to raise awareness about the effects of light pollution by comparing pictures of the night sky from different places all over the world. Once we have collected enough pictures, we will create a digital version that allows a viewer to click on a location to see the picture that was taken there. We will share this digital version online for free. We will happily credit anyone who submits a picture to us, but we will also withhold someone's name if they prefer not to make that public for privacy reasons. "


Looks like a project to raise awareness about excessive light at night, which is a problem for astronomers, for many creatures, especially during migration, and the evidence of one heck of a lot of power being wasted for no good purpose. If people are curious about how badly their area is lit up as compared to other places, they can look at the pictures.


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<p>Thanks, Rose-Marie. </p>

<p>I guess I'm still holding my objection in using astrophotos to illustrate light pollution.</p>

<p>I don't think seeing conditions will substantially improve even in the absence of light pollution in densely populated areas due to increased air pollution. </p>

<p>One of many examples is contrails created by heavy air traffic in major cities turning into cirrus clouds which do not readily disperse, then add a layer of smog at lower altitudes and we end up with atmospheric particulates that becomes difficult to see through. Scattering of light on these particulates that we know as light pollution can also be substantially reduced by using filters during observation. <br>

[<a href="https://www.google.ca/webhp?sourceid=chrome-instant&ix=seb&ie=UTF-8&ion=1#hl=en&output=search&sclient=psy-ab&q=light%20pollution%20filter&oq=&aq=&aqi=&aql=&gs_nf=&gs_l=&pbx=1&fp=c4126340f3b2a615&ix=seb&ion=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&biw=1440&bih=813">Link</a>] </p>

<p>I don't know if increased awareness is going to make much of a real difference as population increases. We'll probably never again enjoy the dark skies we once had, but better use of energy and more efficient use of lighting can certainly help. </p>

<p>I had a conversation with a 90 year-old senior who told me that he would often lay on the grass as a child and see the milky way from a major city. This was at a time when the global population was 1.5 billion, so the odds of every having that experience for future generations is probably slim to none. </p>

<p> </p>

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<p>If you're not convinced that a city full of lights does, indeed, mask out the view of a starry sky, just take a look at comparison shots taken from the downtown of any city or large town taken on a "normal" night and one taken on a night when the power has gone off. One heck of a difference. I just hope that population doesn't expand too much next door to me, plenty of useless lights blazing even in this semi-rural area. I just bought a 10 inch Dobsonian telescope today and assembled it, I want to make some use of it. Now...if these darned clouds would just shove off, I could play with my shiny new toy!</p>
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