Researchers bundle 24 400mm lenses into a massive telescope array


An international team of researchers have grouped groups of 24 Canon EF 400mm f/2.8 lenses together in what they call the Dragonfly Telephoto Array to capture photos of distant stars.

The Dragonfly Telephoto Array is a telescope equipped with several Canon 400mm f/2.8L IS II USM lenses. The telescope array was designed in 2013 by the team, also called Project Dragonfly, which is an international research team from Yale University and the University of Toronto. The Dragonfly Telephoto Array is capable of capturing images of galaxies so faint and so large that they had escaped detection by even the largest conventional telescopes. Its mission is to study the universe at low surface luminosity in order to elucidate the nature of dark matter and to use the concept of distributed telescopes.

Project Dragonfly lens set viewed from the side at night
Image by Pieter van Dokkum, Yale University
Project Dragonfly lens set viewed from the front
Dragonfly Telephoto Array installed in New Mexico | Image by Pieter van Dokkum, Yale University

“The Dragonfly Telephoto Array is the ultimate survey telescope for finding faint, diffuse objects in the night sky,” the researchers explain. “It has allowed us to discover ultra-diffuse galaxies and other low-surface-brightness phenomena, rendering images that deepen our understanding of how galaxies form and provide key insights into the nature of dark matter. .”

Set of Project Dragonfly lenses being assembled
Assembling the Dragonfly Telephoto Array – the first three lenses

In support of this research, Canon provided technical support by supplying 40 Canon EF 400mm f/2.8L IS II USM lenses in 2015, which extended the range to 48 lenses, with 24 lenses grouped on two separate mounts. Since then, the research team has produced significant results in extragalactic astronomy, including the discovery of the ultra-diffuse galaxy Dragonfly 44 in 2016 and the identification of a galaxy devoid of dark matter, NGC 1052-DF2, in 2018.

Project Dragonfly lens set viewed from the front at an angle
The Dragonfly Telephoto Array before 2015

Canon will extend its support for the project and provide technical assistance to the team as well as additional 120 EF 400mm f/2.8 IS II USM lenses, adding to the initial batch supplied six years ago.

Set of Project Dragonfly lenses seen from the front at night
Image by Pieter van Dokkum, Yale University
Sample photo taken by Project Dragonfly with the moon shown to scale
Photo taken with the Dragonfly Telephoto Array. The moon is shown to scale. | Image by Pieter van Dokkum, Yale University

“With the addition of 120 of these lenses, in a newly developed configuration allowing the use of extremely narrow filters, Dragonfly will be the most powerful wide-field spectroscopic line-mapping machine available,” the researchers say.

“One of the main goals of the next iteration of the Dragonfly network is to detect and study the faint gas thought to exist around and between galaxies. By opening this new window into the cosmos, Dragonfly will address some of the most critical questions of astrophysics today.

Project Dragonfly Lens Set Group
Rendering of the full range of 168 lenses that will be built

With a total of 168 lenses, the telescope array has a light-gathering capacity equivalent to that of a refractor telescope 1.8 meters in diameter, with a focal length of just 40 centimeters. Canon and Project Dragonfly expect this additional capability to “open new windows into the universe.”


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