B737-700 FIRST OFFICER TURNED THE WRONG WAY DURING SID DEP DUE TO CONFUSION IN INTERPRETATION OF THE RMI HEADING INDICATION.

Narrative

WE WERE CLIMBING RWY HEADING (057 DEG) OFF OF RWY 6 OFF OF BIRMINGHAM. ABOVE 10000 FT; WE WERE HANDED OFF TO ATLANTA CENTER. AROUND 12000 FT; AND STILL CLIMBING; WE WERE CLRED DIRECT TO ATLANTA. SADLY; THE EFIS RMI IN THE CLIMB OUT (WITH CORRECT FREQ) WAS POINTING TO THE WEST. I STARTED THE TURN TO THE LEFT. IN THE TURN; THE RMI #2 WITH ATC VOR IN IT; STARTED TO NOW SHOW THE OPPOSITE WAY; EAST. CAPT TOLD ME THE FMC COMPUTER WAS NOW INDICTING TO 080 DEG TO ATC. WE WERE AT A HEADING OF 350 DEGS; I IMMEDIATELY TURNED BACK TO 090 DEGS TO GO DIRECT ATC. WHILE TURNING BACK TO 090 DEGS (TO GO ON COURSE); ATC CENTER ASKED ABOUT OUR HEADING. CAPT RESPONDED BACK TO ATC THAT WE GOT OFF A LITTLE BIT; BUT WE ARE ALREADY CORRECTING. ATC RESPONDED VERY SMART ALEC WISE; 'MORE THAN A LITTLE BIT.' ATC SAID NOTHING MORE ABOUT IT. I THOUGHT THIS OVER MANY MULTIPLE TIMES WHAT I DID WRONG. FIRST OFF; I COULD HAVE USED THE MOVING MAP TO VERIFY WHERE TO GO. (SADLY DURING THIS TRIP SERIES; WE USED OLDER PLANES WITH NO MOVING MAP TILL THIS TRIP. YOU GET USED TO THAT IT WAS NOT THERE.) I COULD HAVE CHECKED HEADING TO ATC WITH THE FMC COMPUTER. VERIFY ROUTING WITH CHARTS. I DID; BUT GOT SUCKERED WITH RMI POINTING THE WRONG WAY INITIALLY.