Thanks everyone! What a response, I wasn't expecting this
David, subframe exposure was 150s ISO1600 @ f/3.5 (total of 16+11 frames for left/right panel). I've always been a little weary of doing long subs and rather opting for higher ISO, but the D800 is proving to be very capable. I think next time I will go for longer subs. The galactic core is easy to process with the ~30min exposure, but definitely need 60min+ on the faint outliers (i.e. Rho Ophiuchi).
Another clear weekend up ahead so hoping to expand this mosaic, see if I can get the blue horsehead nebula & Vdb 99
Thanks again everyone for the feedback