STATE GOVT ACFT ON PHOTO MISSION HAS NMAC WITH ACR.

Narrative

DEPARTED IND ARPT ON A VFR PHOTO FLT. WX WAS CEILING AND VISIBILITY UNLIMITED. UPON LEAVING IND APCH AIRSPACE I WAS TOLD RADAR SERVICES TERMINATED; SQUAWK 1200. I REQUESTED A FREQ FOR FURTHER RADAR ADVISORY AND WAS GIVEN 124.452; I REQUESTED AND RECEIVED VERIFICATION OF THIS FREQ BUT I COULD NOT MAKE CONTACT. APCH HAD BEEN VERY BUSY AND I THOUGHT RATHER THAN TIE UP THE FREQ WITH FURTHER CONGESTION I WOULD TRY TO GET RADAR ADVISORIES ENRTE TO MONTPELIER; IN. I ASKED ANQ TWR TO SUGGEST A FREQ PASSING OVERHEAD AT 7500 MSL. THIS FREQ WAS FAIRLY BUSY AND I COULD NOT GET A RESPONSE. AFTER TWO ATTEMPTS AT CONTACT; I DECIDED TO PREPARE FOR THE PHOTO RUNS AT 6850 MSL. I HAD NEGLECTED TO CHANGE TRANSPONDER TO 1200 WHEN RELEASED BY IND APCH. AFTER 30 MIN OF PHOTO PASSES I PROCEEDED TO SUMMIT LAKE (10 MI S OF MUNCIE; IN) FOR THE NEXT PHOTO. I MADE A STEEP CLB TO 13100 MSL FOR THE PHOTO. JUST AFTER LEVELING OFF AT 13100 AS I BEGAN TO LINE UP ON SUMMIT LAKE I CAUGHT AN AIRLINE APCHING FROM MY 8 O'CLOCK POS SLIGHTLY ABOVE ME. WE WERE ON CONVERGING COURSES. I IMMEDIATELY BEGAN A DSCNT AND LOST VIEW OF THE AIRLINER AS HE PASSED OVER HEAD. I WOULD ESTIMATE WE WERE 500 FT APART VERT. I WILL MAKE A GREATER EFFORT IN THE FUTURE TO MAINTAIN CONTACT WITH RADAR ADVISORY SERVICE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE ALTS USED WERE REQUIRED FOR PHOTOGRAPHIC PURPOSES. THERE HAS BEEN NO FOLLOW UP ON THE INCIDENT.