Collinder 399 - Brocchi’s Cluster

This image is probably in my 5 top favorite astro images so far. While writing this on a hot summer day, constellation Vulpacula shines brightly above my balcony in the night sky. Here in the Netherlands we often have cloudy and rainy nights, so any clear sky is a welcome opportunity, even during these warm short nights of summer.

This time I pointed my telescope at CR 399, better known as Brocchi’s Cluster or the Coathanger. It’s a recognizable group of stars that kinda resembles a coathanger. Although it looks like an open star cluster, it is actually an asterism. An asterism is a chance alignment of stars that only appear grouped from our point of view from Earth. It’s believed that the ten stars of the coathanger aren’t gravitationally bound to each other and don’t share a common motion through space, which sets it apart from real clusters.

While framing this target I also noticed the opportunity to capture a true open cluster on the right side of the coathanger, NGC 6802. It’s a much more compact and distant and lies around 3500 light-years away. NGC 6802 appears as a small fuzzy patch in the sky when you look at it with a telescope and easy to miss if you’re not looking for it.

I hope you enjoy this image as much as I do. I usually focus on nebulae and galaxies, so working on a star field like this, with both a asterism and real open cluster, was a refreshing chance of pace!