Monitoring Sky-Glow

Three easy ways to monitor the sky.

First – Participate in the citizen scientist Globeatnight initiative, sponsored by the National Science Foundation, as a visual observer. 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 from their respective app stores.

Third – And the only way to participate in the Buffalo River project is to use a sky meter.  We have a few Unihedron sky meters we can loan to persons who wish to help document the skies over the Buffalo River.  If you live near the river, or are planning a trip to the river during a time with no moon, register below and we will get a meter to you.  These are very easy to use.  You can report your data to us and online to Globeatnight where you can see your data added to that of others.

(Note, the dark sky meter app for iPhone proved too unstable in its current form for use on this project.)

For more information on the ins and outs of sky monitoring see Hints and Suggestions below and visit our page on skyglow lingo.

Rotary Ann Overlook, Eilish Reding Palmer

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.  (Not to worry your information will not be share nor will there be a lot of emails.)

Hints and Suggestions

First enjoy it – While it is not necessary you might make your monitoring part of a larger interest by learning about the sky. Here is a list of some interesting astronomy related websites: I would add Earth and Sky: and Sea and sky: Consider downloading a free planetarium program for your computer, such as stellarium: and perhaps one for you smart phone: 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:

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 for a given location and date in several places on the internet, such as: But, easier, just wait at least an hour after sunset.

Avoid the moon – The moon is a bright lady who hogs the sky stage when she is out.  Even a sliver will render your observation useless. 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 – While not important for those metering the sky, 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 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 or you will overestimate the skyglow. During that time explore the sky and enjoy – item 1 above.

Dark Sky Meter – For those using the Dark Sky Meter app, you will also want to be away from artificial sources of light that might impact the sky.  Get twenty or thirty yards away from any local light source.  Also, getting a good “dark” is critical to getting dependable results using DSM system. You need to totally cover the camera lens on you iPhone. Press the lensed into the pants leg on the thigh 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 a magnitude reading of the average 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.

Final thought –
By now it should be obvious that no one is going to make a lot of observations. But a number of people making a few observations here and there will get us where we need to go and be a real contribution. Thanks.