An editorial in a leading science journal once proclaimed an end to amateur science: “Modern science can no longer be done by gifted amateurs with a magnifying glass, copper wires, and jars filled with alcohol.” I grinned as I read these words. For then as now there’s a 10x magnifier in my pocket, spools of copper wire on my workbench, and a nearby jar of methanol for cleaning the ultraviolet filters in my homemade solar ultraviolet and ozone spectroradiometers. Yes, modern science uses considerably more sophisticated methods and instruments than in the past. And so do we amateurs. When we cannot afford the newest scientific instrument, we wait to buy it on the surplus market or we build our own. Sometimes the capabilities of our homemade instruments rival or even exceed those of their professional counterparts.

So began an essay about amateur science I was asked to write for Science (April 1999,, one of the world’s leading science journals. Ironically, the quotation in the first sentence came from an editorial that had been previously published in Science.

In the 11 years since my essay appeared in Science, amateur scientists have continued doing what they’ve done for centuries. They’ve discovered significant dinosaur fossils, found new species of plants, and identified many new comets and asteroids. Their discoveries have been published in scientific journals and books. Thousands of websites detail an enormous variety of amateur science tips, projects, activities, and discoveries. Ralph Coppola has listed many of these sites in “Wanderings,” his monthly column in The Citizen Scientist (

Today’s amateur scientists have access to sophisticated components, instruments, computers, and software that could not even be imagined back in 1962 when I built my first computer, a primitive analog device that could translate 20 words of Russian into English with the help of a memory composed of 20 trimmer resistors (

Components like multiwavelength LEDs and laser diodes can be used to make spectroradiometers and instruments that measure the transmission of light through the atmosphere. Images produced by digital video and still cameras can be analyzed with free software like ImageJ to study the natural world in ways that weren’t even imagined a few decades ago. Amateur astronomers can mount affordable digital cameras on their telescopes, which then scan the heavens under computer control.

Cameras, microscopes, telescopes, and many other preassembled products can be modified or otherwise hacked to provide specialized scientific instruments. For example, digital camera sensors are highly sensitive to the near-infrared wavelengths beyond the limits of human vision from around 800nm–900nm. IR-blocking filters placed over camera sensors block the near-IR so that photo-graphs depict images as they’d be seen by the human eye. Removing the near-IR filter provides a camera that can record the invisible wavelengths reflected so well by healthy foliage.

Many of the makers who publish their projects in the pages of MAKE, Nuts and Volts, and across the web have the technical skills and resources to devise scientific tools and instruments far more advanced than anything my generation of amateur scientists designed. They also have the ability to use these tools to begin their own scientific measurements, studies, and surveys. Thus, they have the potential to become the pioneers for the next generation of serious amateur scientists.

Previous installments of this column have covered approaches for entering the world of amateur science, and future columns will present more. For now I’ll end this installment with a brief account of how I began doing serious amateur science so you can see how a relatively basic set of observations of the atmosphere has lasted more than 20 years and, with any luck, will continue for another 20 years.

Case Study: 20 Years of Monitoring the Ozone Layer

In May 1988, I read that the U.S. government planned to end a solar ultraviolet-B radiation monitoring program due to problems with the instruments. Within a few months I began daily UVB monitoring using a homemade radiometer. The radiometer used an inexpensive op-amp integrated circuit to amplify the current produced by a UV-sensitive photodiode. An interference filter passed only the UVB wavelengths from about 300nm–310nm, while blocking the visible wavelengths.

I described how to make two versions of the UVB radiometer in “The Amateur Scientist” column in the August 1990 Scientific American. This article also described how the radiometer detected significant reductions in solar UVB when thick smoke from forest fires at Yellowstone National Park drifted over my place in South Texas in September 1988.

Ozone strongly absorbs UV, and the amount of ozone in a column through the entire atmosphere layer can be determined by comparing the amount of UV at two closely spaced UV wavelengths. This is possible because shorter wavelengths are absorbed more than longer wavelengths.

This meant that my simple UVB radiometer formed half of an ozone monitor. So I built two radiometers inside a case about half the size of a paperback book. One radiometer’s photodiode was fitted with a filter that measured UVB at 300nm, and the second was fitted with a 305nm filter. I named the instrument “TOPS” for Total Ozone Portable Spectrometer. (Full details are at

TOPS was calibrated against the ozone levels monitored by NASA’s Nimbus-7 satellite. This provided an empirical algorithm that allowed TOPS to measure the ozone layer to within about 1% of the amount measured by the satellite. During 1990, ozone readings by TOPS and Nimbus-7 agreed closely. But in 1992, the two sets of data began to diverge so that TOPS was showing several percent more ozone than the satellite.

When I notified the ozone scientists at NASA’s Goddard Space Flight Center (GSFC) about the discrepancy, they politely reminded me that the satellite instrument was part of a major scientific program and not a homemade instrument. I responded that I had built a second TOPS and both showed a similar difference, but this didn’t convince them.

During August of 1992, I visited Hawaii’s Mauna Loa Observatory for the first time to calibrate my instruments at that pristine site 11,200 feet above the Pacific Ocean. The world-standard ozone instrument was also being calibrated there, and it indicated a difference in ozone measurements made by Nimbus-7 that were similar to what I had observed.

Eventually NASA announced that there was indeed a drift in the calibration of its satellite ozone instrument. A paper I wrote about this sparked my career as a serious amateur scientist when it was published in Nature, another leading science journal (“Satellite Ozone Monitoring Error,” page 505, Feb. 11, 1993). Later GSFC invited me to give a seminar on my atmospheric measurements that they titled “Doing Earth Science on a Shoestring Budget.” That talk led to two GSFC-sponsored trips to study the smoky atmosphere over Brazil during that country’s annual burning season, and several trips to major forest fires in western U.S. states.

Going Further

The regular ozone measurements I began on Feb. 4, 1990, have continued to this day along with measurements made by various homemade instruments of the water vapor layer, haze, UVB, and other parameters. In future columns we’ll explore how you can also make such measurements — and very possibly make discoveries of your own.

Forrest M. Mims III

Forrest M. Mims III (, an amateur scientist and Rolex Award winner, was named by Discover magazine as one of the “50 Best Brains in Science.” His books have sold more than 7 million copies.

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