Dragonfly Spectral Line Mapper

Seery Chen, a student at the University of Toronto, got in touch about their Raspberry Pi-powered PhD thesis project: a telescope called the Dragonfly Spectral Line Mapper.

Dragonfly spectral
Dragonfly’s own lighting is giving the starry skies a run for their money

Yes, we’re pretty sure the design is named after real dragonflies due to their cool compound eyes which look like millions of lenses all smushed together.

Dragonfly design inspiration

The design is based on the Dragonfly Telephoto Array, which was developed to find clues to the distribution and nature of dark matter in the universe by imaging faint and spread-out objects in the sky. The original Dragonfly is a telescope made up of a mosaic of Canon telephoto lenses on two mounts. The lenses all point to the same target in the sky: adding together all the images from the mosaic of lenses makes Dragonfly the equivalent of a one-metre telescope. One of those would usually have a starting price of around $500,000.

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An award-winningly abstract shot of the team that is building the Dragonfly Spectral Line Mapper

Looking at intergalactic gas

While the original Dragonfly was built to look at starlight, the Dragonfly Spectral Line Mapper looks at gas. Special filters were added to target a specific wavelength of light, allowing imaging of the “glow” of gas around galaxies. The gas this Dragonfly is looking for is what’s called the circumgalactic medium; this is a huge reservoir of gas and plasma that surrounds a galaxy. The circumgalactic medium can act as a sort of barrier between galaxies themselves and the space between them, which is sometimes called intergalactic space. The circumgalactic medium is really diffused and faint, making it difficult to observe, but the combined strength of Dragonfly’s multiple lenses and the special filters mean that not only can you observe this elusive gas, but you can also take a picture of it.

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The rig lives inside one of these observatory pods at New Mexico Skies, which is basically a campground housing different telescopic projects

Switching in Raspberry Pi

Adding the gas-seeking filters to the original Dragonfly design wasn’t the only change Seery’s team made; they also chose to switch from Intel Compute Sticks to Raspberry Pi. Each lens of the new design acts as an independent subsystem with its own focuser, camera, and Raspberry Pi computer.

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The Raspberry Pis are in the black boxes beside the blue boxes, and both live on the on the back of a camera

Two of the four mounts that will eventually make up the Dragonfly Spectral Line Mapper are built and ready. The final two are planned for completion this summer.

Research papers for further reading

Exciting images of galaxies taken by the Dragonfly Spectral Line Mapper don’t yet exist, but the team’s prototype collected quite a lot of data on the M81 and M82 group of galaxies. You can learn more about it from these two papers by Seery’s colleagues:

NASA also has a short explanation of how the two galaxies have been “locked in gravitational combat for a billion years.” We do love NASA; so dramatic.

Seery has also written up a conference paper about the project, and while the official version is behind a paywall, the preprint version is open access: The Dragonfly Spectral Line Mapper: Design and First Light.

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