Pluto against the stars of the Milky Way

Dwarf Planet Pluto Oct 9th 2011

It was a spur of the moment idea to try and capture Pluto this late in the season before it is lost in the evening twilight as the weeks march on to the winter solstice. Two factors I needed to contend with was a tree blocking my view of the southwestern sky and the immense light dome that is Philadelphia that reaches a third of the way toward zenith. First I needed to wait for the distant dwarf planet to emerge from behind the tree at the corner of my house. In the meantime I refined my polar alignment so locating and verifying the star field would be less of a chore. My final alignment star was Gamma Scuti SAO161520 approx 5 degrees north-north east of the target.

Using my planetarium program Cartes Du Ciel, I slewed the scope to Pluto's coordinates. A quick 5 second exposure confirmed I had the region of interest. I shot 15x30 second exposure and then 15x60 second exposures. Because of the light pollution the 30 second exposures were used.

Its really amazing that I could capture as much as I did considering Pluto was only 14 degrees above the horizon at the time hanging in the mire of light from a large mall and casino approximately 6 miles away. The only naked eye star that I could see in that general direction was Altair. The nearly full moon (96%) was also a factor.

Pluto's position at the time is roughly 4 degrees north of the Sun's future position on Dec. 26th. a few days after the Winter Solstice. At its current distance of 2.9 billion miles, its (reflected) light takes 4.35 hours to reach us. Reflected because the light first had to travel 4-1/2 hours from the Sun.

Here is an WCS overlay of the same image.

A screen image saved from Cartes Du Ciel showing Pluto's position against the stars. My image is overlaid against the chart using the UCAC3 star catalog.

And here is a photo showing the orientation of the scope and camera equipment at the end of the first set of exposures.