M54 – Globular Cluster in Sagittarius

Telescope: Meade SN8 at f/4, Orion Atlas EQ-G
Camera: ZWO ASI071MC, Orion Imaging Skyglow Filter
Sensor Temperature: 0C, Gain: 200, Offset: 50
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 62x60sec saved as FITS
Darks: 32x60sec saved as FITS
Flats: 32x5sec, LED tracing tablet
Average Light Pollution: Red zone, poor transparency, 18 deg. elevation
Lensed Sky Quality Meter: 17.8 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

I came across M54 while on a star-hop across southern Scorpius and up into Sagittarius. In my Meade Mak 7 it was easy to see as a bright, condensed globular cluster.

Until 1994 M54 was thought to be one of hundreds of globulars clusters that orbit the Milky Way in a roughly spherical halo. However, close examination revealed that it is not yet associated with the Milky Way, but instead is part of the Sagittarius Dwarf Galaxy, a small elliptical galaxy that is in the process of merging with the Milky Way, it has even been suggested that M54 may be what’s left of the dwarf galaxy’s core. Either way, M54 is the first confirmed extra-galactic globular cluster.

M54 is located approximately 87,000 light years away on the far side of the Milky Way and contains about 850,000 suns in a sphere about 150 light years across. Globular clusters are relics of the early universe; many are nearly as old as the Universe itself, about 12 billion years old.

-John

M54 (8-15-2017)-2j.jpg