Because even a low-powered green laser is visible at night through Rayleigh scattering from air molecules, this type of pointer is used by astronomers to easily point out stars and constellations.
Green laser pointers can come in a variety of different output powers. The 5 mW green laser pointer (class llla) are the safest to use, and anything more powerful is usually not necessary for pointing purposes since the beam is still visible in dark lighting conditions
Green laser pointers apapeared on the market circa 2000, and are the most common type of DPSS lasers (also called DPSSFD for “diode pumped solid state frequency-doubled&rdquo. They are more complicated than standard red laser pointers, because laser diodes are not commonly available in this wavelength range
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