Organic Astrochemist asked me, "I'm curious, in arriving at this list, about how many objects did you try to observe and found that you were unable to do so?"
Well, I didn't keep track of my failures because I ended up with way more successes than I could've dreamed of. I'd have to say that there might have been 20 that I found but could only make out with the 3-inch mask or none at all. The reason I didn't have too many failures was because I went down "the list" from brightest to faintest and as I got into the 12.0 - 13.0 range I had to make sure to only try for stellar or nearly stellar ones. I plan to do a 75mm list sometime and hope to see as many of the NGC/IC PNe as I can in the coming years.