Different kinds of telescopes have different characteristics. When astronomers Roberto Abraham of the University of Toronto and Pieter van Dokkum of Yale University were studying extremely dim objects with very low surface brightness, they wanted a refracting telescope, which offers fast lenses with with small focal ratios, which is more important than the size of the aperture. But large refracting telescopes are expensive, hard to build and rare compared to reflectors.

So they went off to dinner at a fine Nepalese restaurant in Toronto, downed a couple of Kingfisher beers and got inspired. They realized that there are lots of very high-quality refracting telescopes around, called telephoto lenses. The are long, up to 500mm, and fast at f/2.8 and the latest have terrific nano-fabricated anti-reflective coatings, better than you can find on any astronomical telescope. van Dokkum tells Yale News: "These are the same kind of lenses that are used in sporting events like the World Cup. We decided to point them upward instead."

Instead of buying or building a big refractor, Abraham and van Dokkum MacGyvered up the Dragonfly, ganging 10 of Canon’s best 400mm lenses (at $10,000 a pop on Amazon), added 10 science-grade digital cameras on the eyepiece ends, mounted it all on an off-the-shelf robotic telescope mount and voila: the equivalent of a 400mm refractor (15.7 inches) for about $135,000. (That’s about a quarter the price of an off-the shelf refractor scope.)

The two astronomers — who weren’t quite sure if it would work and even placed a bet on it — wrote in the abstract:

The array’s point spread function has a factor of ~10 less scattered light at large radii than well-baffled reflecting telescopes. The Dragonfly Telephoto Array is capable of imaging extended structures to surface brightness levels below 30 mag/arcsec^2 in 10h integrations (without binning or foreground star removal). This is considerably deeper than the surface brightness limit of any existing wide-field telescope.
They then fed the images of the New Mexico sky into a few Mac minis and they were off, doing “a fully-automated multi-year imaging survey of a sample of nearby galaxies in order to undertake the first census of ultra-faint substructures in galaxies in the nearby universe.” Then back to the restaurant for another Kingfisher. 

This is so clever, taking off-the-shelf parts and virtually duct-taping them into a research-quality scope that’s already doing important work. It's a great example of what architectural critic Charles Jencks called adhocism:

Indeed. Grab some lenses and build a terrific scope that's discovering new galaxies. And these were the first results: “the low surface brightness outskirts of the spiral galaxy M101.” 

first light

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