Your own instruments

A lesson in technology, economics and convenience.

Last week we pointed out that, if necessary, many analog photographers could make their own materials.  Indeed, there is a group of artists who find “alternative processes” more expressive than commercial analog materials and works with them exclusively.  On the other hand, the number of people who could produce digital imaging materials of their own is vanishingly small.  Computer chips are simply not home-workshop items.

One would think that telescopes would be similar to computers, rather than to light-sensitive chemicals.  After all, optical lenses and mirrors must be made to a precise curve; the tolerances are measured in fractions of a wavelength of light.  And yet, for a long period in the last century, most serious amateur astronomers made their own telescopes start to finish. And they were for the most part very successful instruments.

The technological break comes almost accidentally.  The curve one must form for a useful lens or mirror is very close to a sphere, which is what you get automatically from two pieces of glass ground together.  With some patience and a bit of skill (which can be developed, given patience) a worker can form the glass to the desired shape using only various grades of abrasive powder, pitch and a simple testing apparatus.

The motivation was economical.  Commercial astronomical telescopes were expensive, because the market was small and each required much time from a skilled worker.  Meanwhile, most of America was still rural, working the land rather than earning money wages; and during the Depression especially there was precious little cash left over for something as impractical as amateur astronomy.  But someone used to maintaining and repairing farm equipment, and willing to put in plenty of unpaid time, could make an instrument far larger and more capable than he or she could possibly buy.

Instructions on how to do just that were published in a series of articles in the Scientific American, later collected into the venerable Amateur Telescope Making books.  It’s interesting to leaf through them today, with drawings of precision optical testing apparatus made out of kerosene lamps and farm workshop parts.

It was still true well into the second half of the twentieth century that serious amateurs built their own telescopes.  One might start with a small commercial model, but if you were bitten by the bug, you soon found yourself looking at catalogs of glass and abrasives.  You could buy kits rather than putting together your own materials, and your tester used an electric light, but the process was the same.

Toward the end of the century everything changed.  A number of things seemed to come together at once.  First, manufacturing optics became automated, so that even the fearsome curves of the Schmidt corrector plate could be produced in quantity.  Second, there were simply more people, with more disposable income, so there was a market for more instruments.  Third, computer control of nearly everything made things that had been expensive much cheaper.  America had begun the century with many home workshops, not much free cash, and log tables.  It ended the century with many fewer home workshops, much more cash, and computers.  Most amateur astronomers now buy everything they need.

One needn’t feel nostalgia for the old situation: many people are amateur astronomers now who would not have been able, or willing, to build their own telescopes.  And if you really want to, you still can.