Globular Cluster Observing List: 190 Globular Clusters

Choose 50 of the 190 and classify how concentrated each one is

• Choose at least 50 of the 190 globular clusters in the program guide.
• Visual: include at least one Challenge object, describe every cluster, and estimate its Shapley-Sawyer concentration class, from I (most concentrated) to XII (loosest).
• Imaging: include at least three Challenge objects and submit images in place of descriptions. No more than five of the 50 can be clusters in other galaxies.
• Log the date and time, seeing and transparency, latitude and longitude, instrument, and a sketch or description.

The full Globular Cluster list, in the League's order, with a page for each object

Sort any column, or type a name or constellation. The type buttons above the map also filter this table. Best is the month the object is highest at 9 pm. Also on lists the other observing lists the object belongs to, so one observation can count toward more than one program where the League allows it.

110 of the 190 are best in summer: plan the list by month

Each bar counts the objects highest in the sky at 9 pm in that month. An object is also well placed in the month before, late in the evening, and the month after, early in the evening.

88 of the 190 are on another list you may already be working

• Herschel 400: 35 of the 190
• Messier: 29 of the 190
• Binocular Messier: 29 of the 190
• Southern Sky Telescopic: 25 of the 190
• Caldwell: 18 of the 190
• Southern Skies Binocular: 15 of the 190
• Urban: 12 of the 190
• Herschel II: 3 of the 190
• Deep Sky Binocular: 1 of the 190

Challenge objects: the faint, the dusty and the far

The Longmont Astronomical Society of Colorado created the program. 81 of the 190 are Challenge objects: faint clusters such as the Palomar and Terzan clusters, hidden behind dust near the center of the Milky Way or far out in its halo, and 37 clusters in other galaxies, in M31, M33 and the Fornax Dwarf, which link to the page for their galaxy.

The concentration class measures how tightly the stars crowd toward the center. Harlow Shapley and Helen Sawyer set up the scale in 1927: Omega Centauri is class VIII, and the loose NGC 6397 is class IX.

More Astronomical League observing programs on Go Astronomy

• Herschel II: 400 more of William Herschel's objects, after the Herschel 400
• Binocular Messier: any 50 Messier objects with binoculars
• Urban: 100 objects for light-polluted city skies
• Bright Nebula: emission, reflection and supernova-remnant nebulae of both hemispheres
• Open Cluster: 100 or 125 open clusters, sketched and classified
• Planetary Nebula: 110 planetary nebulae, from the Ring to 16th-magnitude Abell shells
• Deep Sky Binocular: 60 non-Messier objects for binoculars, the step after the Binocular Messier
• Southern Skies Binocular: any 50 of 73 southern objects with binoculars
• Southern Sky Telescopic: 50 of 100 southern objects, most south of -48°
• Messier objects: the Messier Observing Program, the League's first, since 1967
• Caldwell objects: the Caldwell Observing Program
• Herschel 400: the step before Herschel II