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Comet 273P/Pons-Gambart


 2013 Apr 6

I managed to photograph this comet in a sequence of 61 1-minute exposures but there was a thin veil of cloud, gradually increasing. This means that my star detection algorithm cannot pinpoint the comet against the background caused by distant light pollution reflected off the thin cloud. I had to add a new facility to GRIP to be able to stack the sequence correctly. Here is the result:

Canon EOS 5D MkII, ISO 6400, 61 x 64s = 65 minutes total exposure
254mm aperture Newtonian f/4.8 (f = 1200mm) HEQ5 mount, driven but not guided
2013 April 6 21:33:12-22:54:57 UT
From Rookhope 54.8N 2.1W 330m asl. Rural, almost no light pollution (3 Bortles)
Exposure control by APT (AstroPhotography Tool)

North is to right, preceding downwards.
This image covers approximately 25.8 x 18.4 arc minutes
The brightest star crossing the top edge is TYC 3859 1463 1, mV 11.11
The gap in each star trail is because I had to pause for an obvious cloud to pass over.

The comet has an interesting history. It was "discovered" at the end of last year and given the designation C/2012 V4 (SWAN). SWAN is an imager on the SOHO spacecraft, observing the Sun and the solar wind. It was noticed that the elements of the orbit matched a comet that was thought to be lost: D/1827 M1 (Pons-Gambart). That name means a dead comet discovered in 1827 by 2 French astronomers, Pons and Gambart. It is now officially agreed that this is a periodic comet, with a period of 188 years and therefore not seen since 1827. Hence the new designation.