What are the limits of what can be done with a Dobsonian on a manual base? I have the Sky-Watcher Flextube 250P Dobsonian and the ASI678MC. I've succeed in imaging Jupiter, The Keyhole in the Carina Nebula, parts of the moon and Omega Centauri (which didn't come out well). The main challenge with clusters and Nebulae is finding focus (any touch leads to vibration) and suprisingly most globular clusters are too big for this camera and telescope combination, and finding anything small (like planetary nebulae) is difficult to do manually and even then nudging the scope to keep them in frame is hard and it's easy to lose them. So I want to know, without GoTo tracking, is this kind of telescope limited to planetary astrophotography, or are other targets available? Or do I just need to be more patient to get more integration time? Any tips to make the workflow more efficient?
Here's what I've been able to capture: