a Curved Vane Spider
Diagonal Holder for an 8" Newtonian
While this article specifically addresses a spider and holder for an 8" Newtonian it can be used as a basis for constructing any curved vane spider or secondary holder.
Above are all of the parts you will make or buy except the mounting bolts, washers and nuts used to hold the spider to the tube. The parts shown include the spider, the holder with diagonal mounted, retaining and adjusting knob, shaft washers, spring washers, and central obstruction stop. Of course, you can always buy a holder to fit the hub. There are some nice ones out there. Check to see what various makers use for a central mounting shaft. Some use a 3/8"-16 thread and some use 1/4-20. Europeans will have their own metric sizes to consider. The threaded rod is nice because you can adjust to the correct distance by simply turning it to the next thread position and locking it down with a nut or threaded knob (McMaster-Carr or Reid Supply in the US).
Go to the Spider
Go to the Holder