Sky Glow Survey – How To
Three easy ways to monitor the sky.
First – Participate in the citizen scientist Globeatnight initiative sponsored by the National Science Foundation. Following five easy steps, using only your eyes, you can make sky measurements that will contribute to a world wide light pollution database used by scientist to map and track global light pollution.
The how to is detailed on the globeatnight website. In a nutshell, the site provides a series of charts, for each of several selected constellations, corresponding to different levels of light pollution. The darker the sky the more stars you can see in the constellation best position for observing on a given night. By matching the chart to what can be seen an estimate of the light pollution at that place and time can be made and be reported. The side benefit is that over time an observer will learn the night sky’s principal constellations.
Second – Another group has made a smart phone app that guides you to selected stars and then automates the reporting process to the Globeatnight database.
The app’s principal advantage is it makes more granular observations (to tenths of a magnitude) possible. However, it only goes down to magnitude 5.2, making it only suitable for urban and suburban skies.
The “Loss of The Night” App can be down loaded for either android or iOS phones.
Third – Dark Sky Meter is $.99 app that can turn your model 4S or later iPhone into a sky meter.
Given the low level of skyglow, Dark Sky Meter, or other metering device, will be required to meaningfully participate in the Buffalo River survey project. But, to be truly useful Dark Sky Meter needs to be calibrated. After visiting the website and down loading the app, return here and register, so we can coordinate calibrating your device. This will also make it possible for us to identify your reliable uploaded data from others that may not be calibrated.
Registration – Actually, while it is necessary to register to participate in the Buffalo River project, we would like everyone monitoring the sky by any method to register with us. That way we can share news and advise from time to time.
Rotary Ann Overlook, Eilish Reding Palmer
Hints and Suggestions
First enjoy it – Make your monitoring part of a larger interest by learning about the sky. Here is a list of some interesting astronomy related websites: http://www.top-site-list.com/topsites/astronomy-sites-top-ten/. I would add Earth and Sky: http://earthsky.org and Sea and sky: http://www.seasky.org/astronomy/astronomy-calendar-2017.html. Consider downloading a free planetarium program for your computer, such as stellarium: http://stellarium.org and perhaps one for you smart phone: http://www.businessinsider.com/11-best-astronomy-apps-for-amateurs-2013-10# Take your time, the sky is a big subject. Just learn a little more as you go along. Oh, and visit the Central Arkansas Astronomical website for new observers and check out the first two documents designed to help beginners find their way around the sky: http://www.caasastro.org/new-observers/
Wait until it is totally dark – There are actually three twilights, civil, nautical and astronomical. You can find out the time of each of these at a given location and date in several places on the internet, such as: https://www.timeanddate.com/astronomy/about-sun-calculator.html But, easier, just wait at least an hour after sunset.
Avoid the moon – The moon is a bright lady and will render your observation invalid. Again, you can find lunar rise and set times on the Internet. Globeatnight, makes it simple by designating the evenings during each month when observations should be made so as to avoid the moon. For those using Dark Sky Meter or other metering device, you will learn that the moon is absent from at least part of the evening sky from about three or four days past full until about that past new. It is absent from the morning sky on the flipside of that period.
Dark-adapt – Visual observers need to know that our eyes, unlike a digital camera, actually have two different sets of sensors. One for low and another for high light conditions. The pupil adapts quickly to changes in lighting but the sensor system takes time – up to half an hour to fully adapt. Further, even a brief exposure to a relatively bright light with blue content will reverse the process. So step away from direct sources of nearby light white light, avoid looking at local sources, use red lensed flashlight if need to read or write, and allow at least ten minutes for adaption. During that time explore the sky and enjoy – item 1 above.
Dark Sky Meter – Getting a good “dark” is critical to getting dependable results using DSM system. You need to totally cover the camera lens without leaving foreign substances on it, like fingerprints. A soft opaque foam rubber pad to put over the lense, or a black uninflated balloon on a finger, or pressing the lens into ones pants in the thigh area, should do the trick. With any metering device, take five consecutive exposures and estimate or calculate the average of the middle three – disregarding the highest and lowest. Then take more readings until you get one that would round to the same .1 of the average reading and send that one in. Don’t sweat the second decimal point, in other words. An average of 19.12, would round to 19.1 and so would a reading of 19.07, for example.