The great Hercules globular cluster (M13) is a superb object to view in the night sky. It is composed of about a million really old stars that form a spherical mass, held together by gravity.
It is one of about 200 globular clusters that orbit our galaxy – the clusters are part of our galaxy but tend to reside in a halo around the central galactic bulge rather than in the main galactic disk.
I’ve observed it though my Nexstar 8SE now on several occasions but with different eyepieces. It appears as a slushy snowball of stars that gets denser and brighter towards the centre.
I recently observed it through a high quality, high contrast Vixen LVW 22mm eyepiece and was a bit surprised to see a number of dark channels running through it. “That can’t be right” I thought, “I’ve never seen that before and you don’t see it in pictures of the cluster”.
It turns out I was looking at a feature known to visual observers as “the propeller” – the feature is made up of some relatively star poor regions which are best seen visually, long exposure or stacked imaging tends to fill in the gaps.
Sometimes it’s difficult to navigate through all the hype about eyepieces but so far I’ve found the wide angle views through my Baader Hyperion 31mm modular aspheric and the high contrast views through the Vixen LVW 22mm to be outstanding.