I was quite entranced by Dana de Zoysa's post here that became a
great article on hard-to-spot globular NGC 6749. I have spent the last two nights hunting down unusual globulars.
I'm observing from the suburbs with a 10" SCT, so I'm not going to break any magnitude records. But I had fun, for instance, with NGC 7006 in Delphinus - at 2' and Mag c.11, it's not exactly going to pop like Omega Centauri. My scope was over in the vicinity looking at the Nova.
But my favourite unusual globular was NGC 6717 in Sagittarius. At Mag 9.2 and 3' diameter it shouldn't be a difficult object, and near enough to zenith at the moment. It's a pretty sparse cluster, type X.
The problem is it's only 2' from the Mag 4 star Nu Sagittarii. The glare from the star is quite overpowering. Looking directly, I couldn't see it at all. The two objects actually overlap, so if you move the star, and its glare, out of the field you lose almost all of the cluster too.
The only way I caught it was with averted vision, when it popped into view quite clearly. This puzzled me; I understand (or thought I understood) the principles of averted vision, and certainly use it as a matter of course to bring out detail in faint objects. But I hadn't heard of averted vision being used to capture objects that were drowning in bright glare. But there it was: stare directly at Nu and the glob vanished; move my vision to the side of the field, and out it pops.
I'd love someone else to give it a try and see if you have the same experience.