Decided to add this as a separate file, this is a 3-arm version of my originally 4-armed telescope center dotter. This is because one of my scopes is glued in partially to a holder which has 3 arms, and well, I had to cut off one of my arms to make it work.
arms= does allow for 4 arms (use only 3 or 4, or it will give you not usable results)
mirror_diameter (in mm), center_dot_diameter (in mm), center_dot_hole_diameter (in mm)
For reference, standard US, Office Depot white hole reinforcement labels (about 3 USD, for more than any sane astronomer would need in a lifetime) are about 14.25mm in diameter (9/16 inches)