Green lasers

We bought a bright green laser a few months ago after reading that dogs (and some cats!) will chase them even more readily than the older red laser we already had. The new laser proved to be a great toy for the pets, exactly as advertised — just shine that green dot anywhere on the floor and watch your furry friends have a ball chasing it.

However, when reading an article about air safety, I discovered that there was an entirely different use for these things — you can use it to point out features in the sky. Instead of pointing with your finger vaguely in the direction of Orion's belt, you can point it out directly with the laser. I tried this on a recent evening, and it works stunningly well. I also tried our older red laser, and it worked, but not nearly so well. I'm not sure if that's due to the power difference (the green one is four times more powerful) or something abou the wavelength, or both differences combined. But whatever the underlying physics, the fact is that with the green 500mw laser, you can point out features in the heavens as easily and as precisely as you can point to items on a printed page...

But read the article I linked to above to find out some reasons to be careful with them!