Comet 103P/Hartley (October 2010)

A Speedy Comet Events in the universe are usually measured along scales of millions or billions of years, so most of what humans observe in the night sky seems constant.  Perhaps that is why comets have always fascinated astronomers.  Their relatively rapid orbits around the Sun result in a visible change from one night to the next.    Comet 103P/Hartley (Fig. 1) is a small, faint comet that orbits the Sun approximately once every 6.5 years.  Because of its close approach to Earth during October 2010, its motion against the stars could be observed during the same night.  The fortuitous combination of this close approach and clear skies on two weekend nights (i.e., not having to worry about waking up for work the next morning) provided an ideal opportunity to capture the comet's motion photographically (Fig. 2). ( back to home page)		Technical Notes Camera: Canon 5D Mark II digital SLR camera with Canon 70-200 mm f/2.8 telephoto zoom lens (zoomed out to 200 mm) and Canon 1.4X teleconverter, effective aperture f/4. Telescope mount: camera mounted directly on Losmandy GM-8 equatorial mount with digital clock drive, tracking unguided. Exposure: sequence of 8 exposures of 28 s at ISO 3200 (Fig. 1) and 210 exposures of 60 s at ISO 1600 starting every 2 min (Fig. 2). Processing: aligned and stacked with Nebulosity program (Fig. 1); color correction, contrast adjustment, and cropping with Photoshop; time-lapse frames assembled with Quicktime 7 (Fig. 2).
Fig. 1.  Comet 103P/Hartley (arrow) in the night sky over our house in Cockeysville, Maryland on the night of 2010 October 8 (early morning October 9) at approximately 1:15 am EDT (Oct 9 at 05:15 UTC).  The comet appeared as a faint greenish glow around a denser central nucleus.  The comet's tail is too faint to be visible.  In the upper right is the Double Cluster, a pair of open star clusters (NGC 884 and NGC 869) in the constellation Perseus. Fig. 2.  Time-lapse movie of Comet 103P/Hartley over our house in Cockeyville, Maryland on the night of 2010 October 9 (early morning October 10) from 9:19 pm EDT to 4:17 am EDT (Oct 10 from 01:19 UTC to 08:17 UTC) as the comet passes the star Eta Persei.  Time has been sped up by a factor of 1200 in this time-lapse sequence, which covers 7 hours of observation.  Playing this movie requires web browser support of HTML5 video.

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