British Astronomical Association
Supporting amateur astronomers since 1890

Secondary menu

Main menu

BAA Gallery Picture of the Week

The Double Cluster in Perseus


Expand image

About this observation
Graeme Coates
Time of observation
02/01/2020 - 11:03
Double Cluster
Observing location
Skywatcher Esprit ED80
SBIG STF8300 camera
5.9 Hrs combined LRGB

Also known as h and χ Persei, the Double Cluster (comprising NGC 869 and NGC 884) is a "line of sight" pairing in the constellation in Perseus, though actually they are only a few hundred light years apart. The clusters have a combined visual magnitude of 3.7 and 3.8 and are visible to the naked eye as a fuzzy patch between Perseus and Cassiopeia.

NGC 869 has a mass of 3700 solar masses and NGC 884 2800 solar masses; so the total mass for the complex is estimated in excess of 20,000 solar masses when including an extensive halo of stars. Based on their individual stars, the clusters are relatively young, both 12.8 million years old, with the hottest stars having spectral class B0; NGC884 also has 5 prominent red supergiants including variable RS Per (closest to the centre of the lower cluster).  This excellent rendering of the famous double cluster gets top marks for sharpness and accurate processing.

Image acquisition: Graeme Coates & Paul Tribe
Processing: Graeme Coates

Copyright of all images and other observations submitted to the BAA remains with the owner of the work. Reproduction of the work by third-parties is expressly forbidden without the consent of the copyright holder. For more information, please contact the webmaster.