Orwell Astronomical Society (Ipswich)

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Comet 38P/Stephan-Oterma

Comet 38P/Stephan-Oterma is a comet with a period of 38 years. It was discovered by Coggia at Marseilles Observatory in January 1867 and is currently on its fourth apparition. On 30 November 1980, OASI member Martin Cook found it using the Orwell Park Refractor. OASI member David Barnard had plotted its position on Norton's Star Atlas from BAA predictions and, after a little while, Martin identified one tiny, hazy spot where nothing else should have been. The visible diameter of the object in a 32 mm eyepiece was approximately 0.5 arcmin, the object itself being rather diffuse and seemingly circular. I made a drawing between 20:35 UT and 21:10 UT to show the location of the object and then kept it under observation through intermittent, hazy cloud until 21:44 UT.

When Martin identified the comet, it was in Taurus, more-or-less at maximum brightness, heading north into Auriga. Recent BAA estimates put the magnitude at about 8.3, just a little brighter than the object is in reality. But earlier predictions give a brightness three magnitude fainter, and a position 5° in error - it all goes to show how hard it is to predict the details of a cometary apparition.

Roy Adams