M28

From South Dublin Astronomical Society

M28
Type	Globular cluster
NGC	NGC 6626
Constellation	Sagittarius
Right Ascension	18h 24.5’
Declination	-24° 52’
Magnitude	7
Size	11 arc min.
Image:M28 messier image.jpg

The globular cluster M28, a degree to the northwest of Lambda (λ) Sagittaii (Kaus Borealis), is overshadowed somewhat by the more prominent M22 further east. Both are visible in the same medium to low-power binocular field and this will allow you make some comparisons between the two. M28 appears as a dim hazy magnitude 6.8 spot condensed towards the centre. The visibility of the cluster is very much dependant on sky conditions and summer horizon haze can reduce it to a very feeble glow. It’s worth observing the cluster more than once to get a feel for how atmospheric transparency can impact your views of this, and other, objects. M28 was discovered by Charles Messier in July, 1764. It is heavily obscured by interstellar dust in, and near, the plane of the Milky Way with the most recent distance estimates placing it 18,300 light years away.