Monday, October 25, 2010
I've just received word from the optician that the mirror has been ground and polished, and that he's now in the process of the most important step, figuring it. That's put simply, turning a spherical mirror into a parabolic one so all the light that reflects off of it comes to a single focal point. He'll have to test the mirror to see both the shape of the surface and the progress he's making, and this can require many cycles of figuring then testing to get it right. Although it's taken considerably longer than I expected, figuring a large, short focal ratio mirror is not an easy task for even a professional optician. I would have made the mirror myself if I had a place where I could do the work and had I made several ten or twelve inch mirrors before trying to take on a 15-inch mirror. I opted to leave the job to someone who has the skills I lack, it was quite a project so far when it came to the wood working and welding I had to carry out. I expect a month or so to pass by before the figuring and testing is complete and then the mirror can be coated. Once that is done, it can be shipped and I can then determine the length and angle of the truss poles, pole blocks and pole seats the telescope requires. Then I can make the shroud for the truss poles and then I'll be ready for the moment that has been nearly two years in coming, the first views through a dream telescope I mostly made by myself.