This is an observation from a year ago, together with Matthias Kronberger from the Black Forest in Germany at 1200 m. Conditions were excellent with the Gegenschein being visible. As it is now again the right time for IC 443, I thought I post it here.

Matthias came over from his 15" Dob, suggesting to try the southwestern filaments of IC443. I had tried this one already earlier with my 22" and OIII filter, but without success. Matthias suggested to try the UHC filter, based on similar intensities of this filament in OIII and H beta. And indeed, with UHC at 5.5 mm exit pupil and the conditions given, the filament was not overly difficult. We also observed it in Matthias 15" Dob later on. With OIII filter, the filament vanished.

Here is a DSS image of the filament with four prominent stars framing it