Photo/IllutrationA composite image of 160 shots taken with an exposure time of 10 seconds each shows the night sky full of stars with the North Star at the center over Hidakagawa, Wakayama Prefecture. (Tatsuo Kanai)

Even in a densely populated nation such as Japan where light pollution is prevalent, star watching remains a popular pastime.

In particular, Achi and Minami-Maki in Nagano Prefecture as well as other municipalities, are publicizing themselves as sites from which a bountiful number of stars can be seen in the dark skies overhead.

To help similar efforts, the Environment Ministry developed a system to evaluate how easily celestial bodies can be observed across Japan to allow local communities to promote themselves as prime star-gazing sites.

Under the method, visual observations of night skies in summer and winter and images shot with digital cameras will be analyzed to quantitatively assess astronomical observation areas.

Regions given high marks can use the results to boost tourism.

In addition, it is pointed out that light pollution by the excessive light from streetlamps and building windows at night not only blots out the stars but also leads to a waste of energy and damage to ecosystems.

Starting in January, the ministry will call on a wide range of parties to join the project.

Under the plan, how stars are seen around constellations selected by the U.S.-based International Dark-Sky Association will be surveyed based on visual observations of night skies conducted between late July and mid-August as well as in January.

Images of the zenith taken with digital cameras within two weeks before and after the new moon in January and August will also be used to assess and quantify “the brightness of the night sky.”

The ministry said it will collect data for three years to develop its own evaluation standards based on the association’s gold-silver-bronze criteria.