Going Retro

Abstract

You have to hand it to the refractor. Its unobstructed optics produce the sharpest, highest contrast images of any telescopic design contrived by the artful mind. The earliest varieties, those erected by Hevelius and ­Huygens in the seventeenth century, for example, had enormous focal lengths (F > 60) to remedy the many flaws inherent in a single convex lens. Yet, with such unwieldy “contraptions,” Saturn’s rings were clearly discerned, and the first recognizable Martian surface feature was recorded. In the eighteenth century, the doublet achromatic objective made its first appearance and was slowly perfected over a period of another century, where it reached its quintessentially modern form in the innovations introduced by the genius of Joseph Fraunhofer. The superior optics of the achromatic doublet allowed the focal length of the refractor to be greatly shortened, and for the next 150 years it has retained its iconic form, typically embodied in a F/15 format. Much of the foundation of modern stellar astrophysics were elucidated with such old, high-quality glass. These imposing instruments that continue to decorate our observatories and museums pay testament to the great skill and ingenuity of our telescopic forebears. But in a world full of shiny CNC tubes, broadband multicoatings, and dual-speed Crayford focusers, it’s nice to take a walk down memory lane and re-experience the simple pleasures of a well-made refractor from yesterday. And we’re not just talking about taking a visit to your local public observatory. Sadly, hundreds of thousands of dusty old refractors lie forgotten in our dank and dark basements, attics, and outdoor sheds. Yours truly got to plough his first telescopic furrow with a brazen red Tasco 60 mm F/12 refractor. Back then, I couldn’t pronounce chromatic aberration or astigmatism, let alone understand them. But I didn’t need to, either. That simple refractor changed my life for the better and set me on a path that I’ve yet to tire of.