I have been imaging a series of dim Sharpless objects recently and have really struggled to obtain the OIII data that I require to complete bi-color versions. There has been plentiful Ha (as usual) but even my 30 minute exposures have struggled to collect sufficient clean OIII data, so much so that I have decided to keep my current project (SH2-115) as a mono Ha image! I started to suspect (for a second time) that my Astrodon 3Nm OIII filter was failing so decided to get a reality check on how it was performing. SH2-105 (The Crescent Nebula) is rich in OIII so this made for a good test subject to find out if the filter had gone faulty or not.
The data I captured has settled the argument for me - sorry Mr. Filter, I never should have doubted you!