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Comet C/2011 L4 (PanSTARRS)


 2013 Sep 14

Canon EOS 5D MkII, ISO 6400
254mm aperture Newtonian f/4.8 HEQ5 mount
30 x 32s on 2013 September 14 at 20:10:24-20:29:30 UT
From Rookhope 54.8N 2.1W 330m asl. Rural, almost no light pollution (3 Bortles)

This comet is now 3.7au from us, in Boötes. It was too faint to segment on each individual frame so the comet trails slightly rather than the stars.

 2013 Apr 6

This comet is still not yet high enough to be visible from my observatory, which lies in a valley. So I drove up to the Northumberland/Durham border again with a fixed tripod. I had to wait longer than I expected, to spot the comet in binoculars. The twilight band near the horizon had to almost disappear. I first made contact at about 21:30 BST (20:30 UT). Then I made a quick series of exposures before the comet disappeared again behind bands of cloud near the horizon. The comet is no longer bright enough to be seen by the naked eye.

Canon EOS 5D MkII + Canon 100-400mm L IS lens at 400mm
f/5.6 ISO6400, 50 x 2s exposures stacked in GRIP
Fixed tripod, 2013 Apr 6 20:37:17-20:39:46 UT

 2013 Mar 16

Today there was only a cloud gap along the horizon at sunset. Amazingly it persisted long enough for me to get another photo of the comet, from the same site as yesterday. I took a longer sequence, better focussed:

Canon EOS 5D MkII + Canon 100-400mm L IS lens at 400mm
f/4.5 ISO1600, 196 x 1s exposures stacked in GRIP
Fixed tripod, 2013 Mar 16 19:22:35-19:34:56 UT

I needed binoculars to find the comet in the twilight, which I succeeded in doing at 19:15. Once I knew where to look it was just visible to the naked eye for about 10 minutes, after which it was too low.

At least 4 sixth-magnitude stars in the constellation of Pisces can be seen here as short trails indicating the movement of the comet in 12 minutes. The comet is moving up and to the right (almost exactly due North) which probably explains why the right edge of the tail is more sharply defined than the left.

The tail visible here subtends 20 arc minutes or so. The comet is 1.15au away (1.15 x the distance to the Sun), so the visible tail extends for more than 1 million km.

Pan-STARRS - Panoramic Survey Telescope and Rapid Response System - is an automated system in Hawaii continually scanning the sky to discover new objects. It discovered C/2011 L4, as the name tells, in the second half of June 2011.

 2013 Mar 15

The skies cleared just before sunset so I was able to head out to try to see this comet. I drove to the Northumberland/Durham border, just above Allenheads, in order to get a high view across to the western horizon. I searched the twilight horizon for a long time with binoculars. Eventually, at about 19:05 I caught a glimpse of the comet. It was briefly visible to the naked eye at 19:20 (knowing where to look) but was then becoming very low. Here is the result of combining 47 exposures:

Canon EOS 5D MkII + Canon 100-400mm L IS lens at 400mm
f/5.6 ISO1600, 47 x 2s exposures stacked in GRIP
Fixed tripod, 2013 Mar 15 19:30:02-19:33:29 UT

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