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Thursday, December 29, 2016

Dragonfly Telephoto Array Uses Canon EF 400mm f/2.8L IS II Lens

Dragonfly Telephoto Array - University of Toronto Dunlap Institute of Astronomy

Back in 2014, I reported scientists from the University of Toronto’s Dunlap Institute for Astronomy and Astrophysics created an innovation project for studying the universe using an array of Canon EF 400mm f/2.8L IS lens. Back then, the array used 10 lenses. Now the new setup is using up to 48 lenses and they have graduated to the EF 400 f/2.8L IS II model.

Dragonfly is an innovative, multi-lens array designed for ultra-low surface brightness astronomy at visible wavelengths. Commissioned in 2013, the array is proving capable of detecting extremely faint, complex structure around galaxies. According to Cold Dark Matter (CDM) cosmology, structure in the Universe grows from the “bottom up”, with small galaxies merging to form larger ones. Evidence of such mergers can be seen in faint streams and filaments visible around the Milky Way Galaxy and the nearby M31 galaxy.

But the CDM model predicts that we should see more of this structure than is currently observed. However, images obtained using even the largest, most advanced telescopes today contain scattered light that may be hiding this faint structure.

Dragonfly is designed to reveal the faint structure by greatly reducing scattered light and internal reflections within its optics. It achieves this using ten, commercially available Canon EF 400mm f/2.8L IS lenses with unprecedented nano-fabricated coatings with sub-wavelength structure on optical glasses.

Also, Dragonfly images a galaxy through multiple lenses simultaneously—akin to a dragonfly’s compound eye—enabling further removal of unwanted light. The result is an image in which extremely faint galaxy structure is visible.

The array began imaging targets in 2013 from its home at the New Mexico Skies hosting facility. Images have shown Dragonfly is at least ten times more efficient than its nearest rival and will be able to detect faint structures predicted by current merger models.

Funding for the Dragonfly project is provided by DAA Prof. Roberto Abraham’s NSERC Discovery Grant, with initial funds provided by the Dunlap Institute and Yale University, and an NSERC equipment grant awarded in 2013.

Using this specially designed Dragonfly Telephoto Array, the scientists discovered a hitherto unknown Dark Galaxy. The new galaxy, Dragonfly 44, was named after the project.

"Dragonfly 44 is a dim galaxy, with one star for every hundred in our Milky Way. But it spans roughly as much space as the Milky Way. In addition, it’s heavy enough to rival our own galaxy in mass, according to results published in the Astrophysical Journal Letters at the end of August. That odd combination is crucial: Dragonfly 44 is so dark, so fluffy, and so heavy that some astronomers believe it will either force a revision of our theories of galaxy formation or help us understand the properties of dark matter, the mysterious stuff that interacts with normal matter via gravity and not much else.

The discovery was made by astronomers Pieter van Dokkum of Yale University and Roberto Abraham of the University of Toronto. They did not use Canon sensors, tough. The lenses are mounted on SBIG STF-8300M CCD cameras. The array began imaging targets in 2013 from its home at the New Mexico Skies hosting facility."

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