Secondary holder
The secondary holder in more detail. It is made from two pieces of aluminium strip, one of them bent to an angle of 135°. The two parts slide over an intermediate 6mm steel ball from a ball bearing. This gives a very well defined reference point for all movement. Three screws allow adjustment.
The vanes, made from steel packing straps, are connected to the cage walls by means of modified M-8 lockbolts. The flange of the bolts is sawed/ground off, thus providing enough flesh to cut a slit for the vane and to drill a hole for an M-3 bolt. The spider is very rigid, and the secondary mirror does not vibrate at all, or maybe just a little at a few thousand Hz.
To protect the secondary mirror while stored, i used a length of rainpipe with 4 slits that match the vanes. When the scope is stored, the piece of pipe cannot move, and the secondary cage can be used to put some gear in, such as eyepieces, flashlight, etc...