The Double Cluster
NGC 869 & NGC 884 • Open star clusters • Perseus • 7500 light-years from Earth
🔭
Askar 130PHQ
📷
ZWO 2600MC Pro
🌃
Bortle 8
⏱️
7 hours
🗓️
November 2025
Overview
The Double Cluster is a pair of star clusters in the constellation Perseus. The stars are around 14 million years old and 7500 light-years from Earth.
Background
The weather forecast coming up is terrible, and I didn’t want to start another long-term project knowing that I might be clouded out for weeks. So, I chose the Double Cluster as a target because I’d be able to image it in a single night.
I used 2-minute subframes for this image rather than my usual 5-minute, just to help keep the bright stars under control.
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Science
The Double Cluster is formed, as the name suggests, from two separate star clusters. The one on the left of my image is called NGC 869, while the one on the right is NGC 884. They’re fairly similar, and are useful examples of what happens after a burst of star formation.
Explore the field
Objects in this field 4 objects
4 objects
No matching objects.
- h PerseiNGC 869
- Open clusterAlso catalogued as Cr 24 · Mel 13
- One of the two open star clusters that form the Double Cluster in Perseus.
- chi PerseiNGC 884
- Open clusterAlso catalogued as Cr 25 · Mel 14
- The companion open cluster to NGC 869 in the Double Cluster.
- Double ClusterC 14
- Stellar association
- Caldwell 14 is the combined Double Cluster. Its boundary is a catalogue guide.
- 7 PerseiHD 13994
- StarAlso catalogued as 7 Per · HR 662 · HD 13994 · HIP 10729
About the labels and credits
Positions and outlines are calculated from a plate solution of this photograph. Outlines are catalogue guides and may not follow every visible filament. Additional catalogue objects may be faint or indistinct in this exposure.
Plate solving and annotation data: SkySolver, by Dominik Sito. Stars: Gaia DR3 and Hipparcos (ESA). Deep-sky data: OpenNGC © Mattia Verga (CC BY-SA 4.0), SIMBAD and VizieR (CDS). Names: Wikipedia (CC BY-SA 4.0) and IAU WGSN. Catalogue overlay adaptations, including styling and selected display names, are shared under CC BY-SA 4.0. Photograph © Lee Pullen.
The stars in these clusters contain elements heavier than helium, which astronomers call “metals”. This is a clue that the stars themselves formed from the remnants of earlier stars that shed their material or exploded as supernovae (as those events are necessary to form the elements present within the Double Cluster’s stars). In other words, these stars are made from recycled material!
The Double Cluster contains a few red supergiant stars, such as AD Persei and RS Persei, which I’ve labelled. These have a cooler outer temperature than most of the other stars in the cluster (around 3500K, compared to up to 25,000K for the others). This is why they appear red; as far as stars are concerned, red is a cooler temperature colour than yellow, white, or blue.
These red supergiants are evolved, massive stars. Massive stars can end their lives as supernovae, but the remaining lifetimes of the individual stars labelled here cannot be determined from this image.
Imaging details
- Total exposure
- 7 hours
- Dates captured
- 25 – 26 November 2025
- Location and sky
- Bristol, UK (Bortle 8)
Equipment and software
- Telescope
- Askar 130PHQ Flatfield Astrograph
- Camera
- ZWO ASI 2600MC Pro
- Mount
- Sky-Watcher EQ6-R Pro
- Guiding
- WO 50mm + ZWO ASI 120MM Mini
- Control
- ASIAIR Plus
- Software
- PixInsight, Lightroom
- Image by
- Lee Pullen
Exposure by filter
Optolong L-Quad Enhance
- Channels
- RGB (stars)
- Subframes
- 210 × 2 minutes
- Integration
- 7 hours
View subframe and stack
Single subframe and integrated stack, both with a simple stretch applied.
Kit list
This is the equipment I used to capture the image.
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Telescope: Askar 130PHQ
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Camera: ZWO ASI 2600MC Pro
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Mount: Sky-Watcher EQ6-R Pro
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Guidescope: William Optics 50mm with ROTO Lock
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Guidecam: ZWO ASI 120MM Mini
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Control: ASIAIR Plus
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Filter: Optolong L-Quad Enhance
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