Takahashi's 1.25-Inch star diagonal uses a high quality prism instead of a mirror. This means a lifetime of service where the coatings won't erode. The prism inside the Takahashi star diagonal returns 100-percent internal reflectivity. Its exit and entry surfaces of the prism are multi-coated for minimum light loss.
To protect the barrels of your good eyepieces, Takahashi has designed its star diagonal with a non-marring molded compression ring to hold the eyepiece in place. The compression ring is tightened by a ribbed thread-on grip around the eyepiece which simply turns to tighten its hold on your precision cargo.