Comets are notoriously difficult beasts to predict how bright they may become so any prediction of their magnitude in Nightscenes has to be taken with this in mind. Still it is worth including any known comet that may have a chance at becoming visible in binoculars or even naked eye and, at the time of writing the book, two of them occur for the second half of 2018. So we have Comet 21P/Giacobini-Zinner and Comet 46P/Wirtanen to look forward to with the latter potentially becoming naked eye!.

Comet  21P/Giacobini-Zinner

Comet  21P/Giacobini-Zinner is at mag 8.8 in Cassiopeia on August 1st and is circumpolar for all of the month and into early September. In the top chart it races across Cassiopeia passing Epsilon () C-GZ-sept-oct.jpgCassiopeia on August 12th then into Camelopardalis passing CS Camelopardalis on August 21st. It clips Perseus then enters Auriga as it heads in the direction of Capella. It lies close to that bright star on September 3rd when the comet will be mag 7.1. As it crosses through central Auriga and heads towards Gemini it is no longer circumpolar as it passes the Messier star clusters of M38 and M36. It is then at Perihelion on September 10th before lying close to M37 the next evening.

The comet races past M35 on Sept 16th and is now better placed in the morning sky to view. It moves between Gemini and Orion then into Monoceros passing close to the star cluster M50 on October 8th. It moves into Canis Major passing to the left of Sirius on October 14th/15th and has faded to mag 9.1 on October 26th at the end of the second chart (left)

Here is a wide field image of the comet taken on August 17th with a 200mm lens by Paul on a star adventurer tracking mount and Canon 50D DSLR. Stack of 13 x 2 min exposures at ISO 1000. The nebulosity at right of the image is the Heart & Soul nebula but only a hint of it.

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