visibility of wavelengths?

which is more visible red at 650nm or blu ray diode, assuming both driving at 120 mw?

this will answer your question
http://www.repairfaq.org/sam/laserioi.htm#ioicav2

you should bookmark this site Sams Laser FAQ

Definitely 650nm by far. 405nm is on the edge of our vision, 650nm is pretty squarely red if not red-orange.

At night the beam of a 120mW blu-ray is much more visible than 120mW of red.

okay okay, my answer needs an:

*applies to photopic/day vision only

When your eyes have are applied to photopic vision (day vision) like when you are indoors in a very enlighted room, the red will be much more visible because then the eye is most sensitive to 555nm, and 650 is much closer to that than 405. So then, the blu-ray beam will almost be invisible to your eye. But if you will go into a very dark room and be there for some while, your eyes will adapt to scotopic vision (night vision). Then, your eyes are the most sensitive to (at least I think it is) 505nm, which is much closer to the blu-ray wavelenth, than the red one. So it depends if your eyes is adaped to photopic vision or scotopic.

So go to a dark place at night and be there a while to let your eyes adapt, and then fire up your 120mw blu-ray and reds into the sky. The blu-ray will be much brighter than the red.