Refractor Vs. Reflector: The 19th Century Aperture Race
Yerkes Refractor - Alvan Clark and Sons, 1895
You will never see mention of Aperture Fever in the New England Journal of Medicine. Even so, thousands suffer from this affliction. Pictured at left are a few pathetic victims congregated beneath a 40" Clark refractor- several of them no doubt thinking, "...too late now, but we could have asked him to push it to 50 inches."
What are the symptoms? Well, after buying a telescope have you ever regretted not having purchased the next size up? Did you wonder how much more detail you would see on M42 with a mirror two inches larger than the one you currently use? If so...
Inside astronomy jokes aside, some people have suggested that "aperture fever" is something to be overcome-- as if the symptoms were merely manifestations of a character flaw, an inability to be satisfied with what one has. Unfortunately, that seldom has anything to do with it. The point of astronomy is to study areas of the universe far beyond the Earth and to interpret what we see. The problem, of course, is that the objects are so distant that a great part of Astronomy has always been to push the limits of the equipment and even the limits of our bodies-- our eyes.
Even the associated lexicon has expanded to cover the phenomena. Phrases like "averted vision" and "learning to see" are commonly used. But even before those ideas and accompanying phrases came into play there was still much physical ground to cover in the quest to see the universe. From the time of Galileo's first two-inch refractor to the largest earth-bound telescopes of the 21st century, astronomers have been involved in a 400 year struggle against the laws of physics and the telescope size limitations imposed by those laws. Early in the nineteenth century there came two be two dominant schools of thought regarding the type of optical system best suited for large telescopes: refractors vs. reflectors.
Reflector Telescopes Win By Default
Refractors Halted At 40 Inches
Chromatic aberration had always been the refractor's most glaring defect. But even without its elimination, the images produced were still so sharp that astronomers were reluctant to abandon lenses in favor of mirror based light gathering instruments.
But at 40 inches they seemed to have hit a wall beyond which no one has been able to go, even more than a hundred years later. The problem was the weight of glass and the resultant inability of the lens to keep its shape.
Another seemingly insurmountable problem was chromatic abberation. In other words, when
Largest Telescopes of the Nineteenth Century