Thank you, Malcolm!
I might buy an OIII filter too in the near future.
Yes, I agree that the term "planetary nebula" is confusing.
I think I found the Clown Face Nebula yesterday. (For some reason Starry Night omits the "Face"
in its definition.) It was "just" before it disappeared behind a tree and it was very small, as you said. I was using the 25mm eyepiece by itself and didn't have time to change it because it was really just disappearing. I will try a bit earlier tonight (weather permitting). If I use the filter even if the sky is not dark yet it should be fine.
Later I looked at the sky again with the LPR filter and it was beautiful so dark, even if the stars were a bit dimmer of course.
