Comparing six globs
During my trip to La Palma in June 2018 I finally had a chance to observe these three globular clusters close to eachother at the bottom of the “teapot” for a bit of a longer period. On paper, they are quite alike in size and structure, but in reality it was easy to see the differences. I thought it would be fun to do a comparison sketch so that the differences can be seen at a glance. The observations were done with the 10″ newton at 240x.
M69 – has a bright and triangular core, a bit more stretched to the N-E. It appears grainy, but can’t be resolved. The outer region is short and a bit more grainy, but still can’t be resolved. On the S-E boundary I see a bit of a dark lane.
M70 – has a very small core in the shape of a reversed heart and can’t be resolved. the large halo can be resolved a bit better than that of M69 with averted vision, but I don’t see any individual stars, just a grainy glow.
M54 – is the largest of the three (just) and looks like an elliptical galaxy on first impression. The 1/3 brighter core gradually flows into the halo and only with effort I can see some graininess in here. The halo too flows very gradually into the sky background.
A month later and back at home in The Netherlands I decided to do another comparison. This time it was the turn for Ophiuchus where no less than 6 Messier globs reside. The highest three of them are still nicely visible from my northern latitude. They are all very different, but striking in their own way.
M12 – The smallest one, but with a large and rich halo. Easiest to resolve. Has a diamond shaped core with a somewhat darker region N-E of it. Star chains are numerous and most prominent on the W-side. The cluster is underlined by three bright stars and surrounded by a bit weaker stars in the shape of a “V”, which make it my personal favorite of the three.
M10 – Beautiful. Perhaps a bit harder to resolve. Also here many starchains can be seen flowing away from the core. There is a notable line of brighter stars crossing the cluster in N-S direction and a few dark dustlanes crawling like worms in front of the core. The shape reminds me of an arrow being shot upwards.
M14 – The most condensed one and it’s even a bit hard to see the graininess. Almost perfectly round, just slightly more confined and “pointy” on the E-side. The brightness fades away softly from the not too bright core to the outer region. The halo is short. Only a few stars can be seen blinking up in the core now and then, of which one exactly in the centre. One starchain meanders towards the S-W. Must be a showpiece from a more southern and darker location, but here it remains a bit too dim for my taste.