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Dark Sky Meter Project / ITO, Yoshiharu

Environmental Measurement of Light Pollution by Dark Sky Meter.

Environment of Night Sky

The visibility a star changes depending on the brightness of the night sky. You might have experienced that the stars twinkle a lot when visiting the mountains or the country side and have seen the Milky Way, which you are usually unable to do. Conversely, you might have been surprised not to see the stars easily from a place with a lot of lights of the city and the town. It becomes difficult to see many stars in town because a lot of lights lighten the night sky, whereas you can easily see a lot of stars in the country where the night sky is dark.

You can see something bright in a dark place more easily than in a bright place. For example, when you are looking for a room light on by seeing windows of the building from outside, which is easier, looking for it in the daytime or the evening? It is bright outside in the daytime, so it is difficult to find bright windows from outside. It is dark outside in the evening, so you can easily find bright windows. Something similar happens between the night sky and stars. Light from a star is much fainter than a building window, so recognizing it is more difficult. If the night sky is not dark enough, faint stars can not be seen well.

We can work and live more safely at night by lighting equipments, but it is too bad that we can not see a lot of stars because too many lights make the night sky too bright (Light pollution).

In the research, we find out the night sky brightness of our neighbourhood with the Dark Sky Meter. If many people get together to do this research, we will be able to know the night sky environment in many places and how much light pollution influenced your home town night sky.

This is the Dark Sky Meter!

Dark Sky Meter 2

Dark Sky Meter

Dark Sky Meter is a device that can show the brightness of the night sky as a numerical value by comparing the brightness of the night sky with the brightness of the light emitting diode of the night sky meter. The difference in the brightness of the night sky over a wide range of points, directions, and time can be compared with this device.

You will see the light emitting diode in the centre of the field of view, against the background of the night sky, through the cylinder of the night sky meter. The brightness of the light emitting diode is changed by the current passing through the light emitting diode. It should be bright first, and it is darkened gradually. Then, the value of the current at which the light emitting diode can no longer be seen and becomes the colour of the background sky at that time is read, and this measurement is recorded as the brightness of the night sky.

How to use Dark Sky Meter

Investigate the Night Sky Environment

Things to prepare

Torch with red film (Or, you can paint the light side with red manicure. )、Pen and pencil set、Observing Report Sheet、Dark Sky Meter、Compass、Star map

Research point

It is the best that you measure from the place where you live normally. If possible, it is best if you have a clear view of most of the sky from there.

Weather of the research day

A clear day without any cloud is the best, however, you will not have many observations. Just take notes on the observing report sheet like "In the eastern heavens thin clouds" when there is a cloud.

Research directions of the sky

Make observations at the zenith and in the directions north, south, east and west at ten degrees altitude, using standard stars such as the Pole Star, Mizar, the Cassiopeia γ, Vega Altair Deneb, Pegasi α, Formalhaut Aldebaran Capella, and the Arietis α and record your observations on the Observing Report Sheet. When you can not measure all the directions, just check the direction of zenith. You can measure"The ten degrees" of north, south, east, and west like this: when you stretch out your arm and clench your fist, when your little finger is level with the horizon, then the thumb becomes about ten degrees. Moreover, when when peeping through the Dark Sky Meter, the field of view of the scope is about seven degrees from one side to the other.

Before the research

Sit in a darkened area for a while, to allow your eyes to become dark-adapted. When you need light to write the results on paper or to see a star map, use a red light torch.

Downloads

Instruction for Dark Sky Meter

PDF480KB

Observing Report Sheet

PDF264KBEXCEL20KB

Related reports

Ito, Y. and Takata, T. : Environmental Measurement of Light Pollution by Dark Sky Meter PDF776KB　Miyagi University of Education Annual Reports of Environmental Education (2004)

Articles

2007年9月12日　大崎タイムス　ロ－カル版

「夜空メーター」高評価

13 December, 2005　The Mainichi Local News

Development of a Handmade Dark Sky Meter

11 December, 2005　The Mainichi Newspapers

Notebook

Research results

Under construction

Related Newsletters(JP ONLY)

Letter No.24　Letter No.23　Letter No.21　Letter No.11

Experiments

http://www.hosizora.miyakyo-u.ac.jp

Get a Dark Sky Meter

Please mail us if you can cooperate in the environmental investigation of the night sky.

Dark Sky Meter Project E-mail adress mueit_v01@yahoo.co.jp