A B737-500 CAPT RPTED THAT; AS A RESULT OF FATIGUE AND THE PF'S MISUSE OF THE RANGE RINGS ON THE MAP DISPLAY; THEY MADE A TRACK DEV IN VHHK; FO AIRSPACE.

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WE STARTED A TURN TO A 180 DEG HDG PRIOR TO PRAWN; CONTRARY TO THE SID PROC. AFTER TKOF; I WENT 'HEADS DOWN' MOMENTARILY TO CHK THE SELECTED FREQ BECAUSE I DIDN'T GET A RESPONSE TO MY CALL UP TO DEP CTL. AT THE SAME TIME; THE PF INITIATED A TURN TO 180 DEGS PRIOR TO PASSING THE PRAWN WAYPOINT. APPARENTLY; HE MISINTERPED THE MAP DISPLAY BECAUSE HE FAILED TO RECOGNIZE THAT THE SELECTED RANGE WAS 20 NM VICE 10 NM AND HE MADE THE TURN BASED ON THE ACFT SYMBOL (TRIANGLE) APCHING THE WAYPOINT. FATIGUE AND WORKLOAD WERE CONTRIBUTING FACTORS. THIS WAS A NIGHT DEP; FOLLOWING A 14 HR GND TIME. THE PREVIOUS DAY WE FLEW 2 LEGS; 10 HRS FLT TIME; WITH A 14 HR DUTY DAY. WORKLOAD WAS INCREASED BY THE RWY CHANGES PRIOR TO DEP AND MINIMAL NAV DATABASE. INITIALLY; WE PLANNED AND 'BUILT' A RWY 25L DEP. THEN WE CHANGED TO A RWY 7R DEP DUE TO INFO FROM A NEW ATIS. AFTER ENG START; WE CHANGED BACK TO A RWY 25L DEP WITH WX INFO UPDATED. THESE DEP PROCS HAD TO BE BUILT SINCE THE NAV DATABASE DID NOT INCLUDE THE SID PROCS. GIVEN THAT WE HAD 'BRIEFED' THIS DEP PREVIOUSLY; WE DID NOT EMPHASIZE THE TURN RESTR AGAIN AS WE CHANGED THE FMC ROUTING AND BRIEFED ON THE TAXI OUT. THIS WAS THE FIRST LEG OF A LONG; 2-LEG FLT TO MAUI WITH A FUEL STOP IN SAIPAN. DEP WAS DELAYED DUE TO PAX LOGISTICS AND WE WERE PUSHING TO STAY CLOSE TO SCHEDULE. THE WX AT THE TIME WAS RPTED AS FEW AT 1400 FT AND SCATTERED AT 2200 FT. THE TERRAIN S OF THE RWYS WAS VISIBLE ABOVE THE LOW CLOUD LAYER AT THE TIME OF THE TURN AND THE FACT THAT THE PF WAS ALSO USING VISUAL REFS MAY HAVE CONTRIBUTED TO THE VARIANCE FROM THE SID RESTR. ON INITIAL CONTACT WITH DEP CTL; THE CTLR ADVISED WE WERE TURNING S OF COURSE AND TERRAIN CLRNC WAS NOT ASSURED. DEP CTL DIRECTED A R TURN BACK TO RWY HEADING.