A comparison of the aberrations introduced to a λ/10 Stemmed Mirror and a λ/10 First Surface Mirror when mounted in a kinematic mount. As shown, a Stemmed Mirror stays within λ/10 specification up to 12 inoz of torque (“hand-tight”) while a First Surface Mirror becomes out of specification with a surface flatness of λ/5.
Stemmed Mirrors are mounted to kinematic mounts by a stem on their back surface, resulting in no contact with the edges of the mirror surface.