Astrophotograph of Double Cluster NGC 884 and NGC 869

This astrophotograph shows the two open star clusters, NGC 884 and NGC 869, which are commonly referred to together as the Double Cluster. They are both about 7500 light years from Earth, and are separately by only a few hundreds of light years, occupying a space in the sky about the size of two full moons. The Double Cluster makes a beautiful star field, dominated by about 300 blue-white super-giant stars in each of the clusters, and speckled with a few fine orange stars.

The Double Cluster is in the northern constellation of Perseus, which is (just) visible from the UK all year. Perseus, the constellation’s namesake, is a mythological son of Zeus, and the Greek hero who beheaded the Medusa in addition to other heroic deeds. The Double Cluster represents the jewelled handle of his sword.

This image is a mosaic of two overlapping tiles. My current setup (see below) gives me a field of view (FOV) of 50×30 arcminutes when using a 0.5× reducer, but the useful FOV is actually much smaller due to coma. I therefore needed two images to stich together to capture the whole Double Cluster.


  • 72× 130-s light frames centred on NGC 884
  • 59× 130-s light frames centred on NGC 869
  • Calibration frames from 27 October 2019


  • Explore Scientific ED 102 mm Apo f/7 refractor
  • Sky-Watcher EQ5 PRO SynScan GOTO equatorial mount
  • Altair GPCAM3 290C colour camera (with UVIR window fitted) and 0.5× reducer
  • Altair 60mm guide scope
  • Altair GPCAM2 AR0130 mono guide camera


  • Sharpcap
  • PHD2
  • DeepSkyStacker
  • Photoshop

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