How to find the Double Cluster in the Perseus Constellation (NGC 864 and NGC 869)

The Perseus Double Cluster is quite a spectacular sight for northern hemisphere observers on an autumn or winter evening.

However, to get the full effect you will need a low-powered wide field eyepiece. Otherwise, you will probably only be able to view one cluster at a time. as you can see two clusters through one eyepiece you want to use a low-powered eyepiece I have found that a simple 32mm Plossl eyepiece is great for this target. In fact due to the size of the double cluster this is a great target for binoculars and probably captures the majesty of the sight better than a telescope.

While it looks like the double clusters NGC 864 and NGC 869 are close together, they are in fact a few hundred light years away from each other. In a similar way to most of the constellations in the night sky this is purely a line-of-sight effect. Although both the clusters contain young, hot supergiant suns that are many thousands of times more luminous than our sun roughly 7,500 light-years away from Earth.

How to find NGC 864 and NGC 869

Click to enlarge Double Cluster star chart

To find the double cluster we are going to start with the great sign post constellation Cassiopeia this constellation is also very useful in finding the other objects such as the Andromeda galaxy as discussed in this article.

When looking at Cassiopeia take note of the distance between the stars Navi and Ruchbah. Then go down on three of these distances from the star of Ruchbah you are now in the constellation of Perseus. Going from obvious constellations like Cassiopeia to lesser-known ones is a great way to learn the night sky.

Then scan the vicinity with your low powered eyepiece you should see the Double Cluster easily as the clusters stand out.

To see what the cluster looks like through the eyepiece and how I created a combined images of both clusters I could not get both clusters in a single shot, with my Astronomy Camera and Celestron SE6 telescope, but I managed to take 540 images of the sky around these two clusters to create a combined image, please watch the video below.

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