The zen of telescope making

A strange thing happened last Friday at the telescope making workshop. I actually made negative progress. Yet I’m not annoyed by it at all. I think I’ve discovered the zen of telescope making. Forget the destination and just learn to embrace the process — there are all sorts of worthy things to be learned by experimenting and messing up.

Two Fridays ago I started final figuring on my mirror. My mirror was oblate (the opposite side of parabolic from spherical), so I had a bit of work to do to correct it. I experimented with a figuring stroke that was very heavy on the edges and light in the center. It put me past spherical and towards parabolic, but unfortunately, it also created a depression in the center of the mirror, a defect that can be hard to work out.

So this past Friday I tried some different figuring strokes. I did fifteen minutes of the standard one-third-over-center stroke, the same stroke I had been using for many weeks prior to get to spherical. The central hole widened and became less steep, but did not disappear. So I tried using the star method, where a paper star is put between the pitch lap and mirror and then a weight is placed on top. This is supposed to depress the center of the pitch lap, so that it hopefully won’t wear away the center as much. It didn’t seem to help so much. So I tried a classical W-shape parabolizing stroke modified to spend more time in the center and less time on the edges. My mirror just got more funky, and the hole remained a problem.

At this point I was frustrated. I foolishly decided to try and force things by polishing really hard, like I had done back during initial polishing. I also used a longer stroke, because the shorter stroke I previously used during initial polishing led to my initial oblate shape. Those of you who’ve polished mirrors before know exactly what happened — when I looked at a Ronchi test, I noticed I had developed a turned-down edge. And the central hole was still there. Thus, my mirror was in worse shape at the end of last Friday than at the beginning.

I noticed the seasoned telescope-making veterans at the workshop being very encouraging and complimentary with me. I also remember being repeatedly warned about how figuring was the hardest stage of making the mirror; there’s a whole filing cabinet in the workshop full of the mirrors of people who’ve abandoned their projects. The majority of them quit during final figuring. It’s the first stage where the sense of progress can easily disappear. You’re no longer moving onto smaller and smaller grits each week, and a minor mistake can quickly reverse weeks of prior progress. So the vets, trying to prevent another person from disappearing, never again to be seen in the workshop (and another mirror being added to the filing cabinet), were being extra nice. But I couldn’t help feeling that they were underestimating me.

I’ve learned many things about figuring a telescope mirror, far more through my failures than if I had simply met with immediate success. I’ve learned an important lesson about patience, and how it never pays to try to force things. I still have a good bit of work ahead of me. But I’m content in the knowledge that I have enough patience to see this through, so I’m not too bothered when an entire week or two are wasted. I’ll be finished eventually. That’s why the veterans of the workshop shouldn’t worry about me. I plan to use my telescope for decades, so what does it matter if it takes another month to complete it? The longer I keep working on it, the more I learn about the process, even if it isn’t immediately reflected with progress. Therein lies the zen of telescope making.

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