Astronaut Don Pettit shows how to take long-exposure photos from the ISS

NASA astronaut Don Pettit created his own device to help him take photos of the stars while on the International Space Station — and the results are pretty impressive. In a Reddit thread spotted by Space.com, Pettit describes how he brought a homemade star tracker with him to space, allowing his camera to capture long-exposure photos without the stars leaving any trails behind.

Star trackers are designed to rotate with the Earth — or in Pettit’s case, the ISS — to prevent distortion when taking pictures of the night sky. One of Pettit’s photos, which you can see above, was a 15-second time exposure. He says his tracker completes a rotation every 90 minutes to match the ISS’s pitch rate. “Without this tracker, you can not take photo[s] longer than 1/2 sec without star blur due to the rate of orbital motion,” Pettit writes.

Image: Don Pettit

In a separate post, Pettit notes that aligning the tracker on a moving platform isn’t an easy task, adding that he can currently take up to 30-second exposures “without significant star motion.” Taking photos through the ISS’s windows also presents another challenge. “Looking through 4 panes of glass, two of which are 30mm thick, at an angle makes for some distortion and relative optically induced star motion,” Pettit says.

Image: Don Pettit

If you want to see even more incredible images captured by Pettit, you can browse through them on his Reddit account page, X, and Instagram. Many show what photos from the ISS look like without compensating for its movement.