Optically Center Scope

I just tested that mirror technique on my 2 spare scopes, a Bushnell Banner 3×9 and an Optronics 4x. It took me less than 3 minutes from removing the caps on the adjustment knobs to centering BOTH scopes! And the Banner took a good 2 full turns to center on one axis and the other I needed a penny to turn the knobs with!!
I used a 4″ mirrored candle coaster that had fairly thick glass to do this.
I found by experimenting that up to a point, the thicker the glass is, the better, you not only get more light in to see what you are doing, but the farther out you are from the mirror surface, the more it amplifies the deviation.
I also found that you need to hold firmly to the end of the scope on the glass because any little movement causes the image to shake.
With that said, you will need to also remove any rubber pads that might be on the bottom of the coaster. Best thing is, you can get these things at any Target, Walmart, Goodwill, Hallmark, or candle store…. etc., and you will not have to cut any glass or worry about sharp edges! I also found that clear plastic gives a false image, so use glass.

JBA

Shaky, that sounds very similar to collimating a reflector telescope. Idea sounds solid and I will try that, thanks!

Try using a small mirror, and a piece of small clear glass, e.g. picture frame glass. Place the glass on top of the mirror, then place Objective end of scope on top of the stack. Adjust the two sets of crosshairs that show up……until they are one. Worked for me!!!!