NGC 884 & 869 – the Perseus Double Cluster

Open clusters do not often feature in these pages. No spiral arms, no wispy nebulosity – just stars. About 21,900 of them in fact.

This is also a rarity in these pages, being a naked eye object. It is visible between the W of Cassiopeia and the head of Perseus as a faint patch, depending on sky quality. Binoculars reveal the two clusters in much more detail. However, I decided to image them with my 14-inch scope to see how much more detail could be brought out.

Located about 7,500 light years away in the Perseus arm of our Milky Way galaxy, these clusters are very young in astronomical terms at about 14 million years – far younger than, say, the Pleiades (~100 My).

Being so young they feature numerous blue-white supergiant stars of spectral types O and B, and indeed the clusters are at the heart of the larger Perseus OB1 Association of young hot stars.

This image was captured with around 30 hours’ exposure through LRGB filters.

Equipment: Planewave CDK14 corrected Dall-Kirkham telescope, Finger Lakes Instrumentation P9000 CCD camera, Astrodon filters, Monster Moag off-axis guider with Starlight Xpress Ultrastar Pro guide camera.

Acquisition software: ACP Expert Scheduler, Maxim/DL. Image processing: PixInsight.