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Observation by Alan Snook: Comet C2017 S3 PanSTARRS

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Alan Snook


Alan Snook


2018 Jul 16 - 23:30


2018 Jul 17 - 14:01



  • 0.5m Dobson-mounted Newtonian
  • 17mm Ethos eyepiece x 120

East Kent

Target name

Comet C2017 S3 PanSTARRS


Comet C2017 S3 PanSTARRS

About this image

The comet is unexpectedly big and bright. Comparing it with galaxy M81 which is at a similar altitude, it is somewhat brighter and larger than the galaxy’s core. M81 is 6.8m all in, so I estimate the comet at 7.0m. Comet diameter is about 4 arc minutes. At times it seemed to have an extended oval outline to NW, but this is very difficult to estimate because it fades out to a low surface brightness edge. The coma is a fairly uniform brightness across much of its diameter. No tail, colour or structure was detected.  Motion to the ESE was obvious after 15 minutes. In 30 minutes it moved about 1.5 arc-minutes. The faint star shining through the halo was only spotted at the end of the observation, as the comet moved off it.  

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