The green laser pointer is the preferred laser pointer color for astronomy because green is the most obvious laser pointer color. The reason why green is more obvious is that the human eye is most sensitive to green light. Another reason is the effect of light in the Earth's atmosphere. When the atmosphere scatters, light is visible in the sky, and higher wavelengths scatter more than high wavelengths. Green is a medium wavelength, so it scatters more and is more pronounced than longer wavelengths such as red.