I recently bought a green laser pointer to use as a pointer at
stargazes. I notice that when I turn it on and point it at a nearby
surface, I see two dots: the primary one and a dimmer "ghost" dot. I
have determined that the ghost dot is not an artifact on the lens and
it doesn't move when I wiggle the lens either. Of course, it's not a
problem for pointing to the sky, but it's rather annoying when pointing
to a solid surface. Any idea what it could be?
Cheers,
Joe Heafner
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I presume that he/she has a green He-Ne laser?
It is probably either a bad AR coating, or dirty surface on one of the
lenses, either the output lens from the tube itself, or from a
collimating
lens in front of the laser itself.