Focus looks good. You might get a bit more detail if you had more subs, but fortunately, globular clusters are fairly bright, so getting a good image with 1 sub is possible.
I'd have to be obnoxiously picky to criticize, but if I must, a couple of the stars have a bit of jiggle (or possibly edge issues) and the center of the cluster is ever-so-slightly washed out. A "normal" person would say it is a very good image. I prefer to be normal.
SkyWatcher 10" SynScan Goto Dobsonian, SV106 Guide, ZWO ASI178MC, Svbony SV105, SV305, Pi3HQcam, Pi4, DIY WaveShare focuser, Linux Ubuntu, KStars/Ekos, Carte du Ciel/CCDCiel, AstroDMx_Capture, Siril, StarTools, GIMP
I still think it is the instability of your deck. It will amplify the slightest shaking from wind or someone walking in the house.
Washout means too long exposure. If you want stars, not faint nebulosity, you don't need 800 ISO (how long was the exposure?). Try again with 100 or 200 ISO.
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
It's very good for one sub. If you had many more it would be much better.
Do you have a field-flattener?
RPI 4 B (4Gb) with SMate
Askar FRA400, TPO RC6, Nikon D5500 full spectrum (with IDAS D1 clip-in filter).
ZWO ASI120MM Mini on ZWO 30F4
ZWO ASI224MC-S on Orion 50 mm f/3.2
ZWO EAF x 2
Unfortunately, you lost data by clipping the histogram off left. My guess would be that you lost a lot of stars around the cluster in so doing.
Best to leave all the histogram visible. Control the background by taking more frames and stacking them rather than making it black.