This amazing picture of the Cassiopeia region by Tom O’Donoghue is a mosaic consisting of 25 frames totalling 350 hours (!) of exposure, taken over 4 years.
Each LRGB panel has Hα data and some have added O3 where objects in that area emitted in that part of the spectrum.
Atik 11Meg CCD camera
Takahashi FSQ106ED @ 530mm