Various items relating to the non-optical parts of scopes. A Quick & Dirty Guide to Anodizing Just what we need - more dangerous chemicals to play with! Guide to Aluminum Alloys More than any telescope maker needs to know about aluminum. Eyepiece Barrel and Thread Sizes What size is a 1¼" eyepiece? Exactly? Also lots of tips on tapping threads, C and T-mount sizes, etc. Crayford Focuser Design A design for a Crayford style focuser. Complete with measured drawings and photos. All About Curved Spiders How to properly design a spider with curved vanes to eliminate diffraction spikes.