Last night I looked unsuccessfully for NGC 2392 (Clown Face nebula) and NGC 3242 (Ghost of Jupiter nebula) with my 150 mm f/8 Newtonian under an estimated Bortle level 3 sky. I believe I had the right locations based on Turn Left at Orion and Stellerium but I saw no hint of nebulousity at either low-power (32 mm, 38X) or medium (15 mm, 80X). I had a higher power eyepiece (9 mm, 133X) fitted with an OIII filter but didn't use it because I could not see the planetaries. I also have a 5 mm, 240X that has been disappointing and a 2X Barlow but did not try them.
I just read a thread from 2017 that suggests higher power:
Below is a chart I made using Stellerium and PowerPoint.