With the help of their teachers, Bruce Mellin and Larry Weatherwax, students at the Brooks School in N. Andover, MA, and West Anchorage High School in Anchorage, Alaska, used a special technique, called blinking, to locate the asteroid Pallas on a series of images taken with the MicroObservatory telescopes.
Blinking was used as far back as 1930 to discover Pluto. Through this process, when two images are blinked, stars remain in place as the images are alternately flashed on the screen. Orbiting solar system objects like planets or asteroids betray their locations by shifting with respect to the fixed positions of the stars.
The students used Voyager II, the sky simulation program, to locate the area of the sky in which they expected to find asteroids, and the image processing program, NIH Image, to prepare their MicroObservatory images for the blinking process.
Using the MicroObservatory telescope, they captured two consecutive images of the same region of the sky in which an asteroid was assumed to be located. The images were processed for clarity, and then stacked, which would allow them to be animated, or flipped back and forth between them, creating an illusion of movement, or animation. This process is what we call blinking, as the images are alternately blinked on the screen.
When the images are properly registered, or lined up one on top of the other, the objects in them that have not moved appear in the same places on the computer screen. The students found the asteroid Pallas by noticing its change in position when the images were blinked back and forth.