Below are the rough stages to make the secondary cage.
|The first sheet being cut with a router. Here you cut two identical rings from ply. These become the top and bottom of the secondary, separated by 4 aluminium poles and kydex.|
|Varnishing. You can see the four equally spaced holes for the aluminium poles, and a routed groove to accept the focusor board (bottom left).|
|The other ring is seen here hanging from the ceiling drying. Note the extra blocks on this ring to hold the poles from the mirror box.|
|The focusor board is 15mm ply (as are the rings), routed down to 5mm thick in the centre, drilled and varnished ready to accept the JMI focusor (on left). The focusor is a NGF-DX2 made by Jim’s Mobile Inc The with Flat Base and DFC (Digital Focus Counter)|
|Here is the completed secondary cage, its dry assembled so I can take it apart for varnishing.|
|Final stage is attaching and trimming the kydex.|
|Finally the spider, secondary mirror, and telrad are connected to the cage completing it.|
|You can see the heat rope on the secondary in this image. I simply glued this with transparent silicon sealant and it works well, clearing the mirror in less than 10minutes on a bad night, generally though its clear in 3 to 4 minutes.|
At this point I weighed the whole cage with everything attached. I need an accurate weight for balancing the scope (See the poles section on how this was achieved).