A simple secondary mirror holder for a diagonal mirror . I designed this secondary mirror holder for my dobson telescope building project using a 114 mm diameter primary mirror and a secondary mirror with 25 mm of minor axis.This simple diagonal mirror holder has the basic 3 screws at 120 degrees to tune the tilt of the secondary mirror. Rotation and translation back and forward the telescope tube is achieved thanks to the knob in which an M4 and one central nut m6 nut is housed.It is a simple but efficient design.The photos show the printed holder painted with a flat black paint which looks nicer that way.Additional is also the base part designed for spider vanesblades made of steel straightedge and fixed with m3 nuts