The Caldwell Catalogue is a list of 109 deep sky objects compiled by the astronomer Patrick Moore as a complement to the Messier catalogue. It includes 18 globular clusters, including the two brightest in the sky, namely Omega Centauri and 47 Tucanae.

The collection is heavily weighted towards the southern hemisphere (15 of 18) and fully half of the GCs lie in the deep southern sky below -50 degrees. The northernmost object (C25) lies at 39 degrees north, making the entire collection visible from my observing location in South Australia. Hence a project was born to collect images of the entire set!

The list of Caldwell GCs is certainly varied. Apart from the showstoppers ω Cen and 47 Tuc) it includes one of the closest to earth (C86), one of the most distant (C25) and some in spectacular settings, notably C108 nestled up against the Dark Doodad nebula.