Pluto – Four Night Sequence

Telescope: Meade SN8 at f/4, Orion Atlas EQ-G
Camera: ZWO ASI071MC, Orion Imaging Skyglow Filter
Sensor Temperature: 0C, Gain: 200, Offset: 50
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 40x60sec saved as FITS
Darks: 32x60sec saved as FITS
Flats: 32x10sec, LED tracing tablet darkened with 3 layers of muslin
Average Light Pollution: Red zone, fair transparency
Lensed Sky Quality Meter: 18.5 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

I always try to make an annual pilgrimage to Pluto before it passes onto the west side of the meridian. This year was a special treat as I was able to capture a set of source images on four nights in a row; an extremely rare event in southwest Ohio. This image is a composite of each of the source images captured from about 9:50 to 10:40 local time (about 1h50m to 2h40m UT) on the evenings of August 23rd through the 26th. At this time Pluto was over 3 billion miles from Earth shining faintly at about magnitude 14.2. The feeble reflected sunlight taking 272 minutes to travel all the way back into the inner solar system. Pluto’s apparent motion from east to west (left to right in this image) is something of an illusion. Pluto is actually moving very slowly from west to east, but since the Earth is sweeping past Pluto as it orbits the sun the view from our perspective makes in look like Pluto is moving backwards (retrograde).

Neat stuff.


I have also attached a 4-frame GIF cropped to highlight the motion of Pluto.


Pluto (8-23-26-2017)-1j.jpg