On Oct. 19, 2014, Comet Siding Spring (also known as C/2013 A1) passed within 82,000 miles of Mars. This is an Oort cloud comet discovered Jan. 3, 2013, by Robert McNaught at the Siding Spring Observatory in Australia. The comet nucleus is estimated to be between 400 and 700 meters (0.2 and 0.4 mi.) I took this image one day before closest contact. As sometimes happens in astrophotography, the following night was completely clouded over.

Technical Information       
Date:                       October 18, 2014  ~7PM
Location:                 Green Valley, Arizona
Telescope:              Takahashi FSQ-106EDX
Camera:                  SBIG STT-8300M
Filters:                     Astrodon Gen 2
Mount:                     AstroPhysics 1200
Exposure:                Lum = six 30 sec. exposures, all unbinned
Software:                 Acquisition: Maxim DL 5, TheSkyX, Pinpoint, CCD Commander
                                Processing: CCDStack, PhotoShop CS6 with various plugins

Comet Siding Spring & Mars