Roll over the image to see the movement of Pluto against the background stars in a 48-hour period. It is near the center of this image and moves downward when the cursor is rolled over the image. Its apparent motion was actually very slow during this time because Pluto and Earth happened to be moving in similar directions in the respective orbits around the Sun.

Pluto has a diameter of about 1400 miles (about 1/5 that of Earth), and orbits the Sun at a distance of about 3 billion miles. It takes 248 years to make one orbit, so since its discovery by Clyde Tombaugh in 1930 it has barely made 1/3 of a revolution around the Sun. Pluto has 5 known moons. Charon is about half the diameter of Pluto, whereas the other 4 moons are much smaller.

At about magnitude 15, Pluto is a challenging object to find, but I have seen it through my 18-inch Dobsonian scope. The trick is to have a very accurate map, and to check on consecutive nights to make sure it has moved against the backgournd stars.

Image details:  Each of the two images used exposure times of 4 minutes each of luminance, red, green and blue, taken with an SBIG ST-8300M imager and a 12" Meade telescope at f/6.7.

September 20-22, 2013