Sure, NASA and other space agencies can use high-tech telescopes to spot extrasolar planets (those that don’t orbit the sun), but did you know that you can do the same from your very own backyard? While more elaborate optical devices certainly yield better results, one can now emulate the experience with some DIY gear. Most importantly, those space-seeking Makers will need a DSLR, a 300mm+ telephoto lens, and a star tracker.
“I decided to follow this lead and went shopping for a telephoto lens for my Canon EOS Rebel XS DSLR. With old manual-focus lenses now useless to most photographers, I was able to acquire a 300-millimeter Nikon telephoto lens on eBay for a song (US $92, shipped), along with a Nikon-to-Canon adapter ($17 from Amazon),” IEEE Spectrum Senior Editor David Schneider writes.
Since a number of these items can get a bit pricey, Makers can build their own “barn door” tracker instead using plywood, an [Atmel based] Arduino, a stepper motor along with a few other components.
To drive the tracker, Schneider notes that he extracted a couple of gears from an old inkjet printer, and “attached one gear to a stepper motor and the other to a nut screwed onto a gently curved length of threaded rod. Rotating the nut pushed the doors of the tracker apart.”
The stepper motor is controlled, via a driver board, by an Arduino unit that allows a user to set the rate at which the doors separate.
“Initially, I mounted my tracker on a camera tripod. But I soon abandoned that as being too precarious and built a sturdy wooden platform. The final component of the tracker is a ball head ($18 on Amazon) bolted to the top, which allows me to orient the camera in any direction.”
While constructing your DIY telescope is one thing, picking out and properly pointing the device at a visible star may be a whole another story. In his IEEE Spectrum recap, Schneider reveals that he used the HD189733 as his focal point, which takes place once every 2.2 days.
As soon as the time arrives, start snapping photos and export them to a computer. Using any number of post-production programs, a Maker can measure the brightness of the star over a period of time. If your star is an exoplanet, you should notice the brightness dips. When it’s over, brightness will return to normal.
“Of course, you can’t just look at the images to see the subtle effects of a transit: There are too many confounding influences, such as changes in the transparency of the atmosphere. And the response of a camera’s imaging sensor is seldom uniform: If the position of the target shifts in the field of view (which is hard to avoid over the course of an evening), the amount of light registered will also change, even if there is no actual change in brightness. To compensate, I used free software called Iris, which allowed me to perform the corrections needed to calculate the brightness of HD 189733, as well as four reference stars.”
While spotting an exoplanet in such fashion a few decades ago would have earned you a Nobel Prize, nowadays it’ll at least garner some admiration from your fellow Maker community! Interested in learning more about this out-of-this world, Atmel powered creation? Watch Schneiders video tutorial below, or head on over to IEEE Spectrum’s entire writeup here.