Origins of Technology

                           How far can you see? Making Telescopes

     It wasn't that long ago, that the "Glass Giant of Palomar" - a huge 200 inch 

that's a 16.6 foot diameter piece of pyrex glass about a foot or two thick. It's an 

incredible story itself from casting the glass mirror at Corning, NY to grinding and

 polishing it to protecting it in it's long railroad journey to North San Diego County,

 California from crackpots that might take a shot at it, to the incredible technology of

 it's mount. The whole story is in a book by David Oakes Woodbury - The Glass 

Giant of Palomar - a great read. 

     I read this and many other books like it on  telescopes, the  history and making

 of telescopes as I built my own six inch - that's  a six inch  diameter mirror - 

reflecting "Newtonian" telescope. I ground it by hand! I  still have a

 photo of it. It cost me eleven dollars for parts, including the glass mirror blank and 

glass  "tool" - the disk you grind the mirror to be against. 

     The theory is that if you simply grind one surface against another you will be left 

with either a totally flat surface, or spherical surface whose reflective focal length 

depends on the length of  the strokes you used to grind it. Only it's not so simple.

      They've been doing these  since before the discovery of glass, using metals 

 instead, that produced actually  excellent results in viewing. 

                                           More in Part II