A comet for binoculars

Comet Giacobini-Zinner is visible in our skies at the moment, and in early September it reaches about magnitude 7, making it visible using binoculars from reasonably dark skies and maybe even from the suburbs as well.The comet is about 60 million km away from us, and reached its closest point to both the Sun and Earth on 10 September.  It’s visible in the late evening sky but is best seen well after midnight, as it will have risen higher in the sky. It is quite easy to find in the constellation of Auriga*, whose brightest star, Capella, is easy to spot in the north-east and is one of the brightest stars in the night sky. Look for it fairly low over the north-eastern horizon, and use our finder charts to pick out the comet itself.

It moves from night to night, as the charts show. Look for a faint fuzzy blob. In a good sky you might see that it has a slightly elongated shape as it is showing a small tail. But don’t expect to see anything spectacular.

  • Update 14 September

The comet is now lower in the sky, having passed from Auriga into Gemini on 13 September, and is best seen well after midnight.  During 15 September it passes across the well-known open cluster M35 in Gemini, but the event takes place during daylight as seen from the UK. A detailed chart of the crossing is shown below the main chart. The best time to view or photograph the event from the UK will be before dawn on 15 September.

Finder chart
View looking north-east at 2am BST in mid September from the UK, showing the track of comet 21P


Track of comet 21P Giacobini-Zinner from 2018 September 14 to 23, with north at the top. Stars shown to mag 9.  Click to enlarge. The comet passed from Auriga into Gemini on 13 September and crosses the open cluster M35 during the day of 15 September, as shown in the detailed chart below.


Finder chart
Detailed chart showing path of 21P across the cluster M35 on 15 September, not visible from the UK. Click to enlarge. All charts produced using SkyMap software

You can photograph the comet with a telephoto lens and a high ISO setting by giving short exposures – say about 5 seconds each – and stacking them using software such as Photoshop or Deep-Sky Stacker.

The comet will remain brighter than 8th magnitude for about a month, but gets lower in the sky night by night, so don’t leave it too long to take a look!

Comet 21P
Comet 21P Giacobini-Zinner, photographed on 2 September by Stuart Atkinson