Caldwell 108

Globular Cluster

Constellation:Musca ID:NGC 4372
Magnitude: +7.2 Diameter: 27 light years.
Apparent size: 5 arc minDistance: 19,000 light years.

Globular clusters are spherical concentrations of stars orbiting in the galactic halo, beyond the flat plane of the galactic disc. 157 of them have been identified. They are each composed of hundreds of thousands of very old stars, with a typical star separation of about a light year, although the separation between stars at the inner core is more likely just a third of a light year!

C108 is a fairly typical globular cluster, except for the reddening of its component stars, caused by intervening galactic dust which reduces the amount of light reaching us. It is among the thirty brightest globular clusters and located in the deep south.

The majority of stars in the image are very much foreground objects. The brighter star (far right) is Gamma Muscae, magnitude 3.8 and only 325 light years away. It’s a lot further than any of the foreground stars to the globular cluster.

🤨 I took the image over a month ago – shortly before my surgery – and have not used my telescope since. It weighs in at about 55 kilograms but I am limited to lifting no more than 2.5 kilograms for at least six weeks, of which only four have expired. I’ve missed a few clear nights but hopefully I can get back to normal towards the end of May.

Feature image date:2021-04-02
Exposure:1 hour (16 frames @ 225 sec)
Field of View:1.59° x 1.06° (up is 231 degrees E of N)

Location of Musca Constellation

Location of C108 in Musca

If the hot-linked Astrometry images do not appear it is because the Astrometry website is sometimes off line.

Telescope & Imaging Details

SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.
Field flattener; ZWO Duo-band Hα (656nm) and [OIII] (500nm) filter.
SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.
Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).
Software: Telescope control: Cartes du Ciel, EQMOD, PHD2, Imaging: SharpCap 3.2, Gimp.
Observatory location: 34° South.

Thanks for reading!

Images © Roger Powell

I’m one of the founder members of Macarthur Astronomical Society and current webmaster.


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