1:45 PM - 3:15 PM
[O11-P06] The Best Position for Nightsky Observation in The City
Keywords:star watching, light pollution, Makali’i, analog experiment, urban area
In recent years, only bright first magnitude stars and other objects can be seen in areas with many light sources, such as urban areas. Therefore, the difficulty of astronomical observation in urban areas has become extremely high. This trend is expected to continue in the future, and we are now at the stage of examining methods of astronomical observation in urban areas. Therefore, in this study, an analog experiment was conducted to investigate how much distance from the light of a street lamp, one of the light sources, would allow astronomical observations.
In this experiment, we decided to increase the number of lights that imitated streetlights and to investigate how the best position would change by varying the amount of light. A large piece of cardboard was used to make the experimental apparatus. The camera was placed on the side of the cardboard, and light A, which imitated a star, was placed on the opposite side of the cardboard. The camera exposure was fixed at 180 so that the luminance values would fit into the graph, and a timer was set for 5 seconds. Light B, which imitated a street, was placed 1 cm from Light A. The light was turned on and the cardboard lid was closed for 5 seconds before the camera shutter clicked. In order to distance the light from Light A, this action was shifted every 1 cm until the position of Light B was 20 cm from Light A. Next, the number of lights B was increased to two, and both were placed so that they were at the same distance from light A. This was done 20 times in the same manner as before. The number of lights B was further increased to three, and the same procedure was repeated. Using the graph function of the Subaru analysis software Makali'i, we measured the lowest value of luminance in the valley between the brightness of Light A and Light B on the graph. Using the measurement results of this experiment, a graph was drawn with the horizontal axis representing the distance between Light A and Light B and the vertical axis representing the lowest value of luminance measured. Then, from this graph, it was found that the slope became more gradual as the number of lights was changed. Therefore, the position of the best position is also considered to be farther away.
In this experiment, we decided to increase the number of lights that imitated streetlights and to investigate how the best position would change by varying the amount of light. A large piece of cardboard was used to make the experimental apparatus. The camera was placed on the side of the cardboard, and light A, which imitated a star, was placed on the opposite side of the cardboard. The camera exposure was fixed at 180 so that the luminance values would fit into the graph, and a timer was set for 5 seconds. Light B, which imitated a street, was placed 1 cm from Light A. The light was turned on and the cardboard lid was closed for 5 seconds before the camera shutter clicked. In order to distance the light from Light A, this action was shifted every 1 cm until the position of Light B was 20 cm from Light A. Next, the number of lights B was increased to two, and both were placed so that they were at the same distance from light A. This was done 20 times in the same manner as before. The number of lights B was further increased to three, and the same procedure was repeated. Using the graph function of the Subaru analysis software Makali'i, we measured the lowest value of luminance in the valley between the brightness of Light A and Light B on the graph. Using the measurement results of this experiment, a graph was drawn with the horizontal axis representing the distance between Light A and Light B and the vertical axis representing the lowest value of luminance measured. Then, from this graph, it was found that the slope became more gradual as the number of lights was changed. Therefore, the position of the best position is also considered to be farther away.