I think it would not matter if the dot is centered on mirror 2 when aligning the beam. I just wanted to be 100% sure there’s no benefit for being closer to center on this mirror before moving on. See pic below for current location. Beam hits same spot both near and far so it is aligned.
It absolutely matters. You are on the right track with the two dots being concentric, but now you need to move the mirror to capture it in the center. If you do not, you may be clipping the beam and only sending a partial beam on down the line.
There are two things I’d like to recommend… first take a 9-minute watch of the following video. I did not produce this video, but I have recommended it to many frustrated laser operators. This gentleman demonstrates mirror alignment in a very similar approach to mine, and he uses an open frame DIY built laser machine, which allows you to see very easily what needs to be done. His animations are excellent as well.
Second, after typing the same guidance over and over, I just decided to author a 12-page illustrated guide to help others with mirror alignment. It’s called “Mastering Your Mirrors” and it will walk you through the process of proper mirror alignment, without asking you to chase after the middle of the mirror, back and forth, and back and forth, wasting hours of time, and miles of masking tape. I am currently asking for a $2 donation for this guide, and if you do not find it worthy of your time and investment, let me know and I will make it right. Many have taken advantage of this material, and I am receiving excellent feedback, and even secondary donations.
Thank you! I’ll check out this material
Where does it hit mirror 1 and 3?
On a new alignment, adjust m1 so it strikes m2 center positioned at the short distance. Then move it at maximum distance, should only need a slight adjustment.
Your diagram strike point is so far off center, I wonder if it will align…
Did this work previously or did you have to change out something.
I recommend one of the Russ Sadler videos on the perfect alignment… it’s up to you… I think his is about an hour.
Tons of them out there… pick your poison…
This is an m2 target from both ends of the carriage.