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In the beginning was the barrel. I made my first telescope mirror, by hand in the early 1970's. While I did not have a barrel to walk around, I did have a stand I made. I worked for months on that 8" Pyrex mirror. I don't think I ever got it parabolized, but I got it coated anyway and enjoyed the views from it for years. Aperture fever set in a couple of years later and I got a 12.5" Pyrex kit from Edmund Scientific. I started working on that monster. along with half a dozen students I was teaching Astronomy to. They were all doing 6 inch mirrors. It did not take long for the excitement of the larger mirror to wear off and become drudgery. I was divorced, poorer than a church mouse and could not afford the material to build a mirror grinding machine. Then we had homecoming, and there was a bonanza of lumber thrown away after the floats had been dismantled. I grabbed a few of the better 2 x 8's and took them back to my apartment and built my first machine using that wood and some other parts I had lying around. Not only did I use that machine to grind and polish the 12.5 inch blank, but reconfigured it to drill a hole through the blank - unfortunately my measuring was not that good and besides being off-center, the plug popped out, before I could figure the blank. I worked on that mirror for a few more months before deciding to put it aside for a while. I put it in the refrigerator, on it's pitch lap, with a rubber pitch lap mat holding open the groves. Let's see, that would have been about 1974. That mirror traveled from North Carolina, to Mississippi, back to North Carolina (in a refrigerator), where it stayed for about 20 years. I finally took it out and packed it away in a card board box. One time during that time period, I sent it off to an amateur optician for him to finish the figuring - he gave up before starting. I built another mirror grinding machine (out of welded angle iron) to work on the mirror, but never used it. In mid-2008 the desire to finish the 12.5 inch mirror hit again - this time with a vengeance. I had this urge to not only finish that mirror, but eventually grind something even larger. So with inspiration flowing, I started designing a radical new mirror grinding machine that would run under complete computer control. The machine was designed part by part in AutoCAD, where I also test fit each part together, building the machine from all the individual drawings. I purchased a milling machine I had always wanted and added stepper motors to the X, Y & Z axis, built a controller from parts I had on hand, attached it to an old computer that is now running Ubuntu and EMC2 software. AutoCAD files are converted using Realize to NGC files. The whole system has been a dream.
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01/22/14 |
