A star tracker is a device that can track stars without any regard to how the spacecraft is traveling during that time. Recently, astronaut Don Pettit tested a similar device on the ISS that he built himself.
Astrophotographer Don Pettit
Astronauts come from many professions. They are often scientists, engineers, or pilots. And in the case of NASA astronaut Don Pettit, also astrophotographers.
This is Pettit’s third time on the International Space Station (ISS), and he continues his long tradition of taking incredible photos. His latest photo, an image of stars and several galaxies, demonstrates not only his visual prowess but also his engineering skills — he used a homemade instrument to take that photo.
At first glance, the image may seem pretty typical: you see the stars and the curvature of the Earth, with an expressive orange glow over the surface of our planet. But there is something strange in the photo: the surface of the Earth is blurred, but there are hundreds, if not thousands, of luminaries in perfect focus.
Under ordinary circumstances, such long exposure photos should show stars as streaks in the sky due to the ISS traveling at about 17,500 miles per hour (28,000 kilometers per hour).
Photo with the use of star tracker
But that’s the genius of Pettit. He took his homemade star tracker, a device that rotates the camera to compensate for ISS movement, into space with him. It’s a variation on a tool that astrophotographers on Earth use to take long exposures of the luminaries as the planet rotates under the night sky, compensating for that rotation so that the stars don’t become streaks in the image.
“This tracker rotates at 90 min [sic] period to match the pitch rate of ISS. Without this tracker, you can not take photo longer than 1/2 sec [sic] without star blur due to the rate of orbital motion,” Pettit wrote on Reddit.
The result is an incredibly sharp image of the night sky, showing many more luminaries than is possible with shorter exposures. (Longer exposures bring out more light or, in this case, fainter stars).
Pettit’s other inventions
This is not the first time Pettit has demonstrated his engineering skills on the ISS. In 2008, he developed a weightlessness coffee cup that became the first patented invention in space.
The astronaut was bored with drinking tea and coffee from bags through straws like the Capri Sun — in microgravity, you can’t tilt the cup to pour out the liquid, and if you shake it, it spills out. But Pettit made an open container out of a piece of plastic that uses surface tension to function like a cup on Earth.
“It adds back the dimension of what it’s like to be a human being in a civilized way,” he said in a YouTube video.
Provided by www.space.com
