NGC6121 (M4) in Sco
M4 is relatively large but is not very concentrated, probably the least concentrated of the more conspicuous globular clusters. A line of brighter stars (~mag 11) running North-South through the cluster is notable. Becvar lists d=14' and mag(v)=6.4, Wikipedia d = 26'. At any rate it is easy to find. It is good to avoid Antares when searching for M4 as your red vision is dampened; M4 like most other globular clusters, is rich in old red stars.