Archive for July, 2016

Telescopic Reflections

Friday, July 29th, 2016

The tenth year of my life turned out to be significant. Not only was my youngest sister born that year, but our family moved to Gainesville, Florida so my Dad could fulfill the resident student requirements for a Doctorate in Education at The University of Florida.

My fifth-grade school year in Florida was pivotal, and my teacher was inspirational. She encouraged my interest in science and reading, and she complimented my singing, which had a much bigger effect than I suspect she intended.

In addition to supporting a positive public school experience, my parents encouraged us all to pursue a variety of activities. I remember assembling a crystal radio set from a kit, and running a 15-foot antenna for it between two trees in our front yard. And they encouraged me to join the local Boy’s Club, which was within walking distance of our little rental house.

At the Boy’s Club, I learned to shoot pool, to play “organized” baseball, and to operate a bow and arrow. But the most important activity for me was joining the Telescope Club.

The main project of the Telescope Club was to help each member build his own six-inch, reflecting telescope. Our telescopes were based on kits purchased from Edmund Scientific. The club, and the project, were led by a kind and knowledgeable man whose name I don’t remember, so I’ll call him Mr. Galileo.

As usual, let me explain. The classic collapsible “spy glass” is a refracting telescope. It consists of a lens at each end; the two lenses work together to project a magnified image into the viewer’s eye and onto the retina.

refracting and reflecting telescope sketches

refracting and reflecting telescope sketches

The light sensitivity of a telescope is determined in large part by the diameter of the light-gathering optics. In the case of a refracting telescope, the cost of a large lens of sufficient quality quickly becomes prohibitive for an amateur astronomer.

The solution is found in a different configuration. The reflecting telescope consists of a long tube pointed to the sky, with a concave mirror at the opposite end of the tube from the sky. The concave mirror focuses the gathered light back towards the sky end of the tube, where it encounters a small flat mirror that turns the light 90 degrees, out the side of the tube, and into a small lens.

It turns out that making a large concave mirror is much simpler than making a transparent lens. You start with a flat, circular piece of glass which will become the mirror, and a slightly convex piece of glass, known as the tool. The shape and quality of the tool are not particularly important – the grinding process averages out any imperfections.

You start the grinding process by sprinkling coarse polishing powder on the mirror glass, and adding a few drops of water. Then you gently place the convex side of the tool on the wet, powdered surface of the future mirror.

At this point, the actual labor begins. You move the tool back and forth on the mirror for a few strokes, say ten. Then you rotate the mirror a few degrees, and repeat. And repeat. And repeat. For hours.

After doing this process for several days, you replace the coarse powder with a slightly less coarse powder. I recall that there were about ten different grades. But this was a long time ago, so I could be wrong.

Remembering that I was ten years old at the time, I am amazed that I completed a project that required so much patience. Peculiar.

As I recall, we took the mirror to the Boy’s Club occasionally so they could measure the progress I was making, using a depth gauge.

At about the half-way point, something terrible and profound happened.

I broke the mirror.

Our house was small, as I remember; it might have been white with blue shutters, but that is only a faint recollection. It did have a garage, but I don’t remember a garage door. The house and garage were connected with a narrow “breezeway” — a roof, concrete floor, and screened walls to make a way for the breeze.

My mirror workspace was in the breezeway, on some sort of low bench. We had spread newspapers on the bench to soak up the sprinkled water, and I think I kneeled on the floor next to the bench, pushing and pulling the tool on the mirror as I went through the grinding steps. I don’t remember how it happened, but somehow I caught a piece of the newsprint, and pulled it back, and pulled the mirror with it. Before I could react, the mirror fell to the concrete floor and broke right in half.

Thinking back, I have no recollection of what the mirror kit might have cost, but I doubt we had much extra money at that time. As it turned out, my Dad had traveled to Miami that weekend to attend some sort of educators’ conference. When I showed Mom what had happened, she said, “I guess you better call your Dad.”

I could not predict what my Dad would say. He was a former teacher, school principal, and basketball coach. And a combat-hardened Marine. (Always. There are no “former” Marines.) I recall feeling some trepidation the rest of that day while we waited for him to return to his hotel for the night, so we could call him.

When the time came, Mom dialed my Dad, and I told him what had happened. I had absolutely no idea what to expect. So it was with the greatest relief that I heard him say, “Call Mr. Galileo and ask him to order you a new mirror blank.”

My Dad and I had a mixed relationship the entire time I knew him. From my perspective today, our relationship almost has a Southern Gothic feel. “You’re not a man until your Daddy says you’re a man.” I respected him, and would even say that I loved him. But we had some tough conversations, even when I was a grown adult with children of my own. Some of my ways and my choices did not make sense to him.

But this mirror incident stands out as a shining example of how he always supported me, and encouraged me. That is why I call it a profound event. Even now, half a century later, I can still remember the relief I felt that night.

The replacement mirror blank arrived within a few days, and I carefully but quickly repeated the whole grinding process over the next few weeks, until Mr. Galileo decided that the mirror was ready. He sent it off to have a thin layer of silver deposited onto to the smooth front surface that I had so carefully ground into its concave shape. The telescope kit included an adjustable mirror mount, and we used that to secure the mirror near the end of a piece of stovepipe which we had painted flat black inside and out.

At the other end of the stove pipe, we mounted the lens holder and the small flat mirror that reflects the focused image into the lens. Instead of buying the recommended type of lens (a significant expense, as I recall), Dad unscrewed a lens from an old pair of binoculars, and wrapped some thin plastic around it until it fit snugly in the lens mount.

The kit came with an equatorial mount made of steel rods and galvanized pipe pieces. The metal pieces, when assembled, would connect two pieces of rock-hard maple, that defied the efforts of Dad’s drill and bits. Eventually we managed to get it assembled, attached a couple of pieces of washing machine hose to the base to support the stovepipe, and used some sort of green, Army surplus straps to fasten the stovepipe onto the assembly.

We never did assemble the legs of the tripod. That maple got the best of us. But we were able to use the telescope by C-clamping the base to a whatever bench or stool we could find

One night in the backyard of our temporary Florida home, not long after we got all the pieces assembled, we focused it onto Saturn, and I remember being able to pick out the faint shape of its rings on the tiny image. Wow.

In the years since, I’ve probably used it a dozen times, mostly to look at the moon. It makes for a dramatic view, with the full moon filling the lens, almost too bright to look at.

In 1997, I hauled the telescope, a C-clamp, small stool, and the whole family up to the top of Rattlesnake Mountain in the Ridgecrest Baptist Assembly grounds to view Comet Hale-Bopp. It was a noble effort, rendered slightly less so with the discovery that my binoculars worked just as well.

As far as I know, I still have the telescope and its pieces somewhere. (Search “peculiar” on this site for further evidence.)

For a work-anniversary gift a few years ago, I selected a modern telescope, motorized and programmable. But I don’t use it frequently enough to remember how to work it. It always needs new batteries. And I’ve re-discovered that the best time to view heavenly bodies is late at night when it is cold and clear. A warm bed is pretty stiff competition.

Then there is the rather significant competition from NASA, Hubble, and a collection of dramatic sky-view sources available at the touch of a screen in the palm of your hand.

But there is still something romantic about reenacting scientific discoveries by gazing at the stars. And what better way to do so with a hand-ground mirror, a binocular lens, and a homemade telescope?