Dreyer describes it as pretty rich with little central condensation. Overall magnitude is 5.9, size is 13', stars estimated from mags. Both clusters shine through a rich, variegated Milky Way field. Dreyer describes NGC6522 as bright, fairly large, round, with considerable, gradual brightening toward the middle. Dreyer's estimate of magnitude 16 stars is a little extreme.
More recent measurements list stars from mag.
In this case, the magnitude estimate is relatively accurate, and the cluster harder to resolve than NGC6522. This is perhaps the most exquisite spot in the heavens. Cluster and nebula sit in the powdery Saggitarius Milky Way, in a region sliced by dark lanes. The cluster features stars ranging from pale yellow to blue, plus a brilliant orange star. The contrast with the coal black nebula could not be more striking.