I was starting to look at some slides on the confocal this afternoon, and it looked decidedly questionable. Not only was the staining dimmer than I thought it should be (based on looking at it on the other microscope), but the plain light bits (which are a lot harder to screw up) were also really dim. I checked the amount of oil on my coverslip, and there was plenty, so that wasn’t it. Then I was reminded that the objective might be dirty. OH MY GOODNESS, cleaning made a difference. Those two pictures? Same growth cone, same settings. The other impressive bit? I couldn’t see anything on the objective when I took it off the microscope to clean it. So (note to self) even if it isn’t visibly dirty, it might be desperately in need of cleaning.