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Although I only use binoculars, I detect differences in my unresolved views of globular clusters.

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Me too. There's lots of differences among globulars visible in giant and supergiant binocs.

To start with, some have higher surface brightness than others. As Hrundi suggests, contrast the dim, hazy Class XII NGC 5466 in Boötes with the more concentrated and brighter M3 4° to its west. Another good surface brightness contrast (though they're a bit far apart) is between the very loose Class XI M55 in Sagittarius and the dense Class I M75 to its east.

David Knisely mentions the stellar core of M15 in Pegasus, which is distinctly star-like even in, say, 15x50 binocs. This is one of the "core-collapse" globulars: clusters in which most of the brightest stars, because they are among the cluster's heaviest, have literally sunk into its center. M30 in Capricornus, M62 in Scorpius, and M70 in Sagittarius are other core-collapse globulars. Though best seen with binocs from the southern hemisphere, all three exhibit their stellar core with giant binocs from dark-sky sites.

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No, I mention a stellar core to M5 not M15. M15's core is definitely more concentrated than some globulars, but I do not see a very distinct stellar core there (just something rather small and concentrated). The one in M5 is actually composed of three or four stars in a tight triangle that is difficult to resolve unless the seeing is very very stable and powers in excess of 300x are used. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org

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M5 . . . has a small dense almost star-like core embedded in its brighter central region. That almost nuclear core at really high power (400x and up) is made up of three or four very closely spaced stars in a sort of triangle, but it takes really high power and excellent seeing to resolve it.

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