The Caldwell Catalog is a list of 109 sky objects published by Patrick Moore in 1995 as a complement to the Messier Catalog. The Messier Catalog was developed as a list of objects to avoid when looking for comets, not as a list of the best objects in the sky to observe. Messier did not include many of the sky's brightest deep-sky objects, and only included objects he could see from Paris. The Caldwell Catalog covers the entire sky and includes interesting objects which are not on Messier's list. Both of these lists were compiled for visual use, but both are also convenient lists for astrophotographers.

The Caldwell objects are numbered from 1 thru 109 in order from northernmost to southernmost objects, spanning from +85 to -80 degrees declination. Of course, unless you live near the equator, you are not able to see all of the Caldwell objects from one site. For this poster, I am only including those objects which I can see from my backyard in East Texas, which includes 85 of the 109 Caldwell objects. The higher numbered Caldwell objects are difficult to image clearly from the northern hemisphere because of their low altitude. For example, my image of Caldwell 85 is of an object which only transits a maximum of 6 degrees above my southern horizon.

After imaging both lists, it is interesting to compare the Caldwell list versus the Messier list. In my opinion, the Caldwell list is underrated. If I had to choose only one list to image, it would be a tough choice. Compared to the Messier list, the Caldwell list has about the same number of open star clusters (C-28, M-27) and galaxies (C-35, M-39), but the Caldwell list has less globular clusters (C-18, M-28) and many more nebula (C-28, M-12).   Messier has the more famous objects (highlighted by the Orion Nebula, Crab Nebula, Andromeda Galaxy, Hercules Cluster, Ring Nebula, Eagle Nebula, Pleiades, Whirlpool Galaxy, and Dumbbell Nebula), while the Caldwell list has more nebula, more small scale objects, and more variety of objects (highlighted by the Rosette Nebula, Helix Nebula, Crescent Nebula, Omega Centauri Cluster, Bubble Nebula, Antennae Galaxies, Witch's Broom Nebula, Eastern Veil Nebula, and Centaurus A Galaxy). The entire Messier list is accessible from the Northern Hemisphere, which is a big factor if you live there. However, the Messier list includes more than a few clunker astrophotography objects (e.g., double star, Andromeda satellites, dim clusters) and feels somewhat repetitive as one moves through all of the clusters. The Caldwell list also includes a few less than spectacular objects, but doesn't feel quite as repetitive.

The technical data for the objects of this poster, including location and size, is shown in Revisions R and S.  

If you would like to read more about any of these objects, each of the objects in the poster has previously been uploaded and described individually on Astrobin. They all reside in my Astrobin Caldwell Collection.