a 
b
Figure 3.3.1. The Newtonian secondary assembly is shown in, 3.3.1a. A sheet steel retaining ring was fabricated to secure the 6" secondary mirror in the secondary holder 3.3.1b.
3.3 Newtonian Secondary
A 6" minor axis elliptical flat was purchased from Coulter Optical Company for the Newtonian focus. The Newtonian secondary holder is made of aluminum with a thin, sheet steel retainer. The secondary is holder is mounted in the tube with a 4 vane spider, which is made of 1/8" aluminum sheet. The body of the tube is 4" thin wall aluminum irrigation tubing with two 1/2" rings at each end for added stiffness, Figure 3.3.1a. Figure 3.3.1b shows the 6" secondary and its retainer ring. The retainer is fabricated from thin sheet steel so that it matches the secondary shape. I machined a 1/2 plate in a lathe so that the profile of the plate matched the elliptical secondary.
a b
Figure 3.3.1. The Newtonian secondary assembly is shown in, 3.3.1a. A sheet steel retaining ring was fabricated to secure the 6" secondary mirror in the secondary holder 3.3.1b.
a 
b
Figure 3.3.2. A push pull
arrangement
is used to adjust the secondary mirror, 3.3.2a. The distance to the
adjustment
bolts is long enough to require a special wrench, 3.3.2b.