Orion LaserMate Deluxe

Description

Wave length 630-680
The Deluxe model has a 45 degree polished surface with a hole drilled through it. The outgoing laser beam passes through that hole on its way to your diagonal. If your optical path is out of collimation, the return beam will hit that surface, and reflect back to you.
From the mirror cell end of the telescope, you see an intense red dot on the 45-degree surface. Instead of running back and forth between the two ends of the telescope, you just turn the screws on your mirror cell, and watch the return beam move back and forth. Because the movement is “real time,” you immediately see which turn of the screw moves the return beam in the correct direction, towards the center hole.
The return beam, if everything is perfectly collimated, will hit the output hole—-with just a little diffused laser light, because the return beam has diverged a bit, and doesn’t all fit back through the hole through the diagonal. The return beam doesn’t exactly disappear, but turns into something like a faint symmetrical spray of red.