The reason that Hubble can observe objects of such wildly different sizes is two-fold. First, the distance to an object will determine how big it appears from Earth, so entire galaxies that are relatively far away might take up the same amount of space in the sky as a globular cluster like NGC 1651 that is relatively close by. In fact, there’s a distant spiral galaxy lurking in this image, directly left of the cluster – though undoubtedly much larger than this star cluster, it appears small enough here to blend in with foreground stars! Secondly, images processors can stitch together multiple images spanning different parts of the sky into a mosaic to create a single image of objects that are too big for Hubble’s field of view.