Combating Light Pollution: how best to view the stars

by Dr Paul E Cizdziel

Night-time light pollution can be precisely measured with scientific devices such as a Sky Quality Meter (SQM) or a Spectral Irradiance Meter (radiance values). Such measurements are taken during the new moon phase, to eliminate any contribution from moonlight. Scientists & photographers have grouped the SQM / radiance values into 9 separate classes; known as the Bortle Scale. The most light-polluted cities in the world, such as Tokyo, are ranked as “class 9” which is considered the upper limit. The lowest level of light pollution is ranked as “class 1” (for example being on a boat in the middle of the Pacific Ocean). Light pollution maps can be found on the internet (www.lightpollutionmap.info) to determine the value for your home area.

The map illustrated here is overlayed with the Bortle scale light pollution index.  The center of Tokyo is Bortle class 9 and areas of green or yellowish are closer to Bortle class 4, where night-viewing of stars is amazingly enhanced.

In my opinion, the most easily accessible and best night sky viewing areas around Kanto include Jogashima Island (Miura), the Eastern & Southern coast of Chiba and nearly all of Izu. These areas are all considered Bortle class 4, where you can see hundreds of stars! Of course, going north or west into the mountains is also dark, but views are often inhibited by greenery or mountain peaks. Furthermore, each of these coastal areas have access to ocean horizons, which are even much darker, offering beautiful views of the Milky Way core in the South during the summer season.

In the winter, the Milky Way core cannot be seen from Japan, but there are many bright and beautiful stars, constellations and planets visible.
The skies are often clearer in the winter time here, as well. At this time of year (currently), the four brightest planets can be observed; Venus, Mars, Jupiter and Saturn. And the majestic Orion constellation and Pleiades star cluster (Suburu) shine brightly now and for many more months.

Constellation Binoculars - These are low-power (2x) binoculars with a 54mm diameter lens that gather and concentrate light to your eye.  As a result, star brightness is amplified more than 10-fold and many more stars are visible, even in Tokyo.  I bought this Sky Rover brand, and highly recommend them.  These kind of binoculars usually cost ¥10,000 to ¥15,000.

I have two recommendations for sky viewing that complement each other.

One is to purchase a pair of constellation binoculars, which are low-power binoculars like the SkyRover 2x54 design. In this case, the number 2 means 2x power, and the number 54 is the lens diameter in millimeters (called aperture). Constellation binoculars have extreme widefield views increasing the star brightness incredibly and allowing more than ten times the number of stars to be seen (even in Tokyo).

My second suggestion is to download a smartphone app that offers augmented reality views of the night sky, enabling anyone to identify specific celestial objects and instantly have information available regarding it. Or vise-versa, use the app to find the location of an object of interest……like Saturn.

My personal favorite app is SkySafari, which is great for astrophotographers and telescope users. But there are many others available, too. Either of these suggestions (or both) might make a nice Christmas present in the coming season. Feel free to contact me at the school if you need more details.

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A note from our Science Advisor, Dr Paul E Cizdziel

The Ad Astra room on the 10th floor of Laurus International Primary & Secondary School is primarily dedicated to space science education, an increasingly important part of modern education. This field of science covers everything from amateur photographers (like myself), to aerospace engineering, government agencies, research institutions, and a rapidly expanding and opportunity-rich commercial sector. My intention with this blog is to periodically provide information of general interest to students and parents on current topics across all these categories.