Erm... this is embarrassing, but I am about 90% certain that it is something in my optics.
Earlier that night I saw something faint while looking at Acrux through a new eyepiece while getting my alignment started. At the time I didn't think too much of it and didn't actually notice it till I finished processing yesterday. No filter was used here which is why I'm perplexed as to why the image came out quite as red as it did. Maybe the Nikon D800 has more sensitivity in the deep reds than some other DSLRs which seem to produce a more purplish nebula.
I did have on my to do list to take some test images on Thursday of a few really bright objects and narrow down if the dot was my optics, and if so which part of the optics.
Failing that maybe I just found my first UFO