In 1958, Dr George Abell compiled a list of galaxy clusters using POSS1 plates consisting of 2712 galaxy clusters (limited to -27° and above). Later in 1989, Dr Abell and Harold Corwin added an additional 1361 clusters. For this guide, the author has selected over 80 Abell galaxy clusters for intermediate and advanced observers with a large telescope (a 16" or larger telescope is recommended).