In the parlance of photography, it’s called capturing the “decisive moment,” the split-second when the composition, emotion and technical elements come together in a perfectly timed image. You know it when you see it. Photographer Mike Eliason, 54, has been capturing decisive moments for the past 30 years, as a photojournalist, public information officer and hobbyist, earning a reputation as a top-tier photojournalist.  At 5:30 p.m. Tuesday at Chaucer’s in Loreto Plaza, Eliason, an interminable introvert with a big smile and jolly disposition, will experience yet another special moment, but this time, he’ll be in front of the camera, with all eyes looking looking at him. Eliason will sign copies of…