Jul 3, 2010: Pluto crawls across the sky

Michael Richmond
Jul 5, 2010

A recent issue of Sky and Telescope magazine pointed out that although Pluto is moving through a very rich star field in Sagittarius this summer, it will pass in front of a dark nebula for several weeks, making it much easier to find. I decided to try my luck at taking pictures of this elusive little planet.

The setup was:

• Meade LX-200 12-inch telescope
• no focal reducer, so working at f/10
• SBIG ST-8E CCD camera with no filter
• 30-second guided exposures

It was easy to find a guide star in this very rich part of the Milky Way.

Notes from the night

• The conditions were good: clear during the entire run.
• The FWHM was around 3.2 pixels. The guider did a decent job; it stuck in Declination for the first few images in the sequence, but then was able to move properly in Dec.
• I took a series of 21 images; each was 30 seconds long, and I paused 270 seconds between images, so it was roughly 5 minutes between images.

Here's one of the images, zoomed in by a factor of two. North is up and east to the left. I've added an arrow to help you find Pluto.

Note the nearly star-free region running vertically down the middle-right portion of the image. There is a dark cloud in the Milky Way which is blocking the light from stars behind it. Fortunately, Pluto is in front of this cloud :-)

Over the course of the 100 minutes that I watched, Pluto moved very slowly. It drifted to the right (west), gradually moving away from a background star. Click on the picture below to watch an animated GIF of the sequence.

Last modified 7/05/2010 by MWR