Following in footsteps of Lord Rosse

By Tom Burns - Stargazing

During my graduate school days four decades ago, I built a telescope designed to see the spiral structure of galaxies. Its $1,000 cost exceeded my starving-student means, so I saved my money for two years. Another year passed while I waited impatiently for the 17.5-inch diameter mirror to arrive from its manufacturer.

When the mirror finally arrived, I pounded the telescope together out of cheap plywood and scrapped cardboard tubing in one frantic weekend. Then I slapped on a coat of leftover house paint.

I was not, am not, and will never be a skilled artisan. The telescope looked awful.

But it functioned just fine, thank you very much. During my long wait, I had built, poorly, 20 or so smaller telescopes, selling one to afford to make the next.

Those ‘scopes resolved the cloud bands and the Great Red Spot on Jupiter. They made globular star clusters explode into thousands of fully resolved stars.

But that was not nearly enough. My secret desire, my overriding mission, was to see the pinwheel-like structure in spiral galaxies with a telescope I had built myself. I wanted to tread the path William Parsons, third Earl of Rosse, had trod 150 years before.

Galaxies may contain hundreds of billions of stars, but they are exceedingly far away. Seeing their structure requires a telescope of sizeable light-gathering power, which in turn requires a large-diameter mirror ground and polished to a paraboloidal shape within an accuracy of .0000002 inches across its entire surface. Thus, virtually the entire cost of my telescope went into a commercially made mirror.

The same telescope mirror would have cost a king’s ransom just 100 years ago. Giant telescopes weren’t available by mail order. The avocational pursuit of stargazing was only for the wealthy, who had the cash and the leisure time to spend on the universe.

Such was the case with the third Earl of Rosse. Born in Ireland in 1800, he served in the British Parliament from 1823-1834. He did so more out of lordly duty than anything else.

What is an affluent member of the ruling class to do when he can retire from public life at the tender age of 34?

Lord Rosse decided to pursue astronomy, and he had the money to do it in a big way. On the grounds of Birr Castle in the center of Ireland, he built the largest telescope in the world.

He had little help in doing so. Circumstances forced him to train the workers on his estate to be telescope technicians.

In those days, astronomers cast telescope mirrors from speculum metal, a mixture of copper and tin. Rosse constructed an enormous forge in which he created a mirror blank with an unheard-of diameter of 72 inches.

Once he cast the blank, Rosse had to develop new methods for grinding and polishing it to the correct shape, a daunting task he finally completed after many months of back-breaking labor.

But that arduous effort was nothing compared to mounting the mirror in a telescope.

He set its tube between two enormous stone walls. In that configuration, he could move the telescope only up and down but not side to side.

Luckily, the stars move, rising and setting like the sun and the moon. Rosse simply waited until exciting parts of the universe appeared directly in line with the mirror. He was, if nothing else, a patient man.

The telescope, called the Leviathan of Parsonstown, was finally ready in 1845. Almost immediately, Rosse began to observe the “starry nebulae,” mysterious, faint patches of light. No one had been able to figure out precisely what they were.

Rosse’s telescope revealed what no other telescope on the planet could see. Some of the faint fuzzies resolved into spirals of light that looked for all the world like children’s pinwheels.

Rosse’s efforts were critical to our comprehension of the larger universe, but they were just as significant to our understanding of our cosmic neighborhood, the Milky Way.

The Milky Way is our very own galaxy, so you’d think that by the 19th century, astronomers already knew a lot about it. The trouble was that they were in it. Its proximity, size, and density made it difficult to estimate its structure.

Simple naked-eye observation reveals that it is disk-shaped and that we are near the perimeter of the disk. That’s what makes it look like a streak of light across the sky.

However, astronomers discovered much more about our galaxy’s overall structure and functioning by looking at other galaxies than by observing our own.

A prime example is M33, sometimes called the Pinwheel Galaxy, in the constellation Triangulum, the Triangle.

M33 is nothing special compared to nearby galaxies. Containing only 60 billion stars, M33 is dwarfed by our Milky Way, which boasts 400 or so billion, and the Andromeda Galaxy, with perhaps a trillion stars.

M33 is also considerably smaller in volume than its larger cousins. At only 60,000 or so light-years wide, it pales in comparison to the 100,000 light-year diameter of the Milky Way and the 150,000 light-years of the Andromeda Galaxy.

However, because M33 is a member of our Local Group of galaxies, it is only 3.2 million light-years away.

Moreover, it is tilted from our perspective so that we see it face-on. Its proximity and tilt make it a prime target for those who seek the spiral structure of galaxies.

Eagle-eyed stargazers claim to have seen M33 with their unaided from extremely dark rural locations. I am not as sharp-sighted as that. In binoculars, it looks like a small, oval fuzzy patch to the west of the most acute tip of Triangulum’s triangle.

Rosse drew the spiral structure of M33 and other galaxies, sometimes with startling accuracy and sometimes, frankly, not so much.

Here you will find Rosse’s drawing of M33:

And so it was that on a crisp autumn evening, I set up my brand-new telescope, the Colossus of Clintonville, on the grounds of the Richland Astronomical Society’s observing site near Mansfield, Ohio.

I had observed M33 many times before in smaller self-constructed telescopes. So it was with practiced ease that I pointed the ‘scope in M33’s direction.

And I gasped. There it was — the faint, fat S-shape. Rosse’s drawing of M33 matched my own first experience with heart-palpitating precision.

Rosse had discovered a fundamental characteristic of the cosmos, but he was left with a more profound mystery than the one with which he started. The “starry nebulae” went from unidentifiable fuzzy patches to unidentifiable spirals. He still didn’t know what they were or why they were spirals, and nobody else could figure it out either.

The answer wouldn’t come until more than half a century after Rosse’s death in 1867. Using even larger telescopes and advanced research techniques, astronomers like Edwin Hubble finally determined that the pinwheels were island universes, galaxies of hundreds of billions of stars separated from each other by unimaginable distances.

But there I was, with a telescope I had slapped together in my garage, tracing out the spiral arms that Rosse himself had seen for the first time over 150 years ago in a telescope the size of an 18-wheeler. And I was one up on the venerable Earl. I knew what they were.

It took me a couple of years to save the $590 to buy that telescope mirror. I endured a full year of waiting while an optician prepared my mirror. At the time, the three years seemed a lifetime. A lifetime later, the wait seems like nothing at all.

We have our troubles these days, no doubt about it. But measured against Rosse’s time on Earth, our times seem glorious indeed.

Fellow and sister stargazers, count your blessings. We live in an age that allows even hoi polloi like you and me to see and understand, albeit incompletely, the glories of the universe.

By Tom Burns


Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.