I'd recommend using fairly low power (roughly 100x) to first identify Palomar 11, which is situated just 4' southeast of a mag 8.6 star. Look for a low surface brightness, patchy glow (many stars will be nearly resolving). High power can definitely resolve a number of the mag 15 and fainter stars in a 20-inch. As far as the details, here are a few of my more recent observations ...
24" (7/25/14): this relatively bright Palomar appeared fairly faint, but fairly large, ~3' diameter. Contains a brighter 1.5' central region that was partially resolved at 260x. At 375x, the core contains roughly 5 or 6 brighter mag 14.5-15 stars and an additional 10-15 faint mag 15-16 stars including several within the central 45". A number of stars in the halo sparkled on and off with averted vision or were close to each other, so counting was difficult.
24" (9/7/13): at 200x this relatively bright Palomar globular contained a brighter core and a roundish halo ~2.5' diameter, with several mag 15 and fainter stars resolved. Well resolved at 375x and 500x into roughly two dozen mag 15/16 (several extremely faint) stars resolved in addition to 5 brighter mag 14.5-15 stars. The resolved stars are distributed over the entire glow, though more concentrated in the 1' core that is slightly elongated SW to NE. Situated 4' SE of mag 8.6 HD 186496 with several brighter mag 12-13 stars scattered outside the halo of the cluster.
18" (7/14/07): swept up at 150x as a very low surface brightness hazy region, ~3' in diameter with a few mag 15+ stars superimposed. Cradled by three mag 13 stars close southwest, east and northeast. A 22" pair of mag 11.5/12 stars lie ~3.5' N. The observation was interrupted before I could use higher power to resolve.
18" (8/2/05): easily picked up in the field at 115x. At 160x appears as a fairly large, very low surface brightness glow, perhaps 3.5' diameter though the periphery fades into the background and is not easily traced visually. The cluster is nestled adjacent to a group of mag 13 stars and a 22" pair of mag 12 stars is to the north. The surface brightness is irregular or mottled and several extremely faint stars pop in and out of visibility at this power including a few stars near the center. Located 4' SSE of mag 8.6 HD 186496.
18" (7/19/04): at 225x, appears faint, moderately large, round, ~3'-3.5' diameter with almost no central brightening although the globular fades around the periphery. Several faint stars are superimposed. It was difficult to estimate the size as the halo is not well defined. At times I felt the diameter was as large as 6' but usually only appeared 3' at best. At 435x, a half dozen faint stars are superimposed though some may be foreground stars (the brightest cluster members are mag 15.5). The cluster's surface brightness is quite low at the magnification.