Caroline’s Rose Cluster (NGC 7789) in Cassiopeia

Recent issues of my favourite UK Astronomy Magazine, Astronomy Now, include a review of deep sky objects within the perimeter of a particular constellation. I like to extract these pages every month and keep them for future reference. When looking for new targets last month I came across the article covering Cassiopeia. I hope the magazine doesn’t mind me reproducing a page in this blog.

A great astronomy resource!

I’ve found that the WO GT81 can produce excellent pinpoint images of star clusters, and the article offered a couple of options that appealed: the well known Owl cluster (NGC 457) and Caroline’s Rose cluster (NGC 7789). The former is very popular so I chose the latter! Besides being a path slightly less trodden, NGC 7789 has a local connection to where I live. The cluster is named after Caroline Herschel, who along with her brother William, discovered many objects from a garden in the town of Bath, which is only about a 45 minute drive away.

In the late 18th and early 19th century Caroline emerged from the shadow of her famous sibling to become an accomplished discoverer of nebulae and comets. In addition she clocked up other finds, including the cluster bearing her name, in 1783. Her 1802 catalogue was later to evolve into the New General Catalogue in 1888.

So here is my record of the night’s plan:

Cassiopeia imaging notes

The excellent Stellarium showed me the way to the target before leaving the house:

NGC 7789, as shown in Stellarium

My framing shots taken at high ISO allowed me to centralize the target, after which I setup the laptop to capture a series of 40, 30s images at ISO 1600. A single frame and then a stacked from are shown below.

NGC 7789, single 30s from using the William Optics GT81

After Deep Sky Stacker followed by Curves and Levels in Paintshop Pro, and finally a slight cropping, here is the result:

NGC 7789, stacked from 40 x 30s sub-frames.

I like that the cluster’s 16 arc-minute dimensions can be framed by neighbouring stars within the EOS’s frame, with no standout members hogging the limelight. It makes a pleasing target.