It seemed to remain the same size for what seemed like several minutes, then very, very suddenly it increased in size and had a green and a red light at the edges.
Part of my normal pre flight check is "camera and battery".
I took several shots of this object (as you do - when everything else is churning along nicely).
I do not use the stabiliser on my camera so I got these views of what I think was a Beech 1900 inbound from Hokitika.
It passed about 3000ft overhead.