The adjust-set II (Concenter) consists now of a closed cylinder, similar to the Cheshire
eyepiece.
The crucial difference with the Cheshire is the let in circular disk with concentric circles.
The Concenter is now out of one "casting", with 2" or 1 ¼" insert diameters, generally
for all focusers usable.
You do not need to make center markings on the secondary-mirror to adjust it.
The adjustment is made directly on the edge of the mirror that results in perfect alignment
of the optical light surfaces corresponding to the offset of the secondary mirror.
You can adjust more precise than with a laser!
Here the principle of the ‘film box’ finds place, established by a disk with concentric
circles. This offers a beginner astronomer an easy possibility to adjust his telescope in a
perfect way.