How to correctly align "be seen" lights My "be seen" bicycle light is bar mounted and has to be reattached every time I jump on the bicycle, due to theft risk.  How do I determine when it is correctly aligned?

In particular how are "be seen" lights correctly aligned so they don't blind on-coming traffic, but so that they're best visible from a distance for on-coming traffic?

This question is primarily about how to adjust beam position for courtesy and safety, rather than the mechanics of mounting any particular light.

related question: How to correctly align &quot;to see&quot; bicycle lights?
With "be seen" lights good ones have a very wide beam pattern so they can be seen from all angles, which makes precise orientation less relevant. If you look at Nathan's bike light database most of those lights are about 180° horizontal beam spread and 90° or more vertically. Again, the better ones have a more even beam spread so there's really no "hot axis" that gets more light.

So I mount them for convenience. I look for somewhere I can attach them where they won't get bumped and point more or less along the axis of the bike, and more or less horizontally. Clipping them into the back pocket of my jeans rather than my belt, for example :)

If you have a poorly made "be seen" light that has a real beam and poor spread, the only real solution is to buy a better one. If you're using an old "see by" LED light in flash mode for this, I suggest setting it up as a "see by" light (per answers to your other question), and using it that way.

If it's particularly bright, the polite thing to do is turn it off or use a lower brightness setting when you're on the bike path. On roads the oncoming traffic should be some way out of your path so blinding shouldn't be an issue. If it is (really narrow roads, for example), I point mine down when I see oncoming traffic. Or turn them off. I have dyno lights that are always on, so turning the blinkie off doesn't break the law or make me invisible.

With my "see sense" lights that are designed to mount to a vertical tube and are annoyingly bright, I mount the front one to my head tube right under the stem so that I am shaded by the stem. That also helps a little with the upward part of the beam, but the real solution is to turn them down at night. It seems a bit odd, but a "daylight visible" flashing light is scary bright at night. So I run them on the lowest power setting at night (maybe ~30 lumens rather than the ~200 lumen peak). I can still see it lighting up reflective signs at 100m, so it's visible enough.