AT A NON TWR ARPT; PVT PLT OF A MOONEY M20J MADE AN IMMEDIATE R TURN AFTER TKOF TO AVOID A C150 COMING HEAD ON 1 MI AWAY. THE RPTR ANNOUNCED HIS POS BEFORE TKOF AND AGAIN WHEN HE OBSERVED THE C150 AND MADE AN EARLY TURN TO AVOID HIM. THE C150 PLT ADVISED THAT HE WOULD FOLLOW THE MOONEY IN THE PATTERN.

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AFTER RETURNING TO MY HOME FIELD AT APPROX XA30 ON A RECENT EVENING; I WAS PRACTICING NIGHT LNDGS. WHILE IN THE PATTERN FOR MY FOURTH LNDG FOR RWY 3; I HEARD A CALL FROM A CESSNA; '5.5 NM TO THE NE; LNDG RWY 3;' AT OUR ARPT; PETER O'KNIGHT. I LOOKED FIRST IN THE DIRECTION THE PLT SAID HE WAS COMING FROM; AND THEN IN ALL DIRECTIONS; BUT EVEN THOUGH THE VISIBILITY WAS IN EXCESS OF 15 MI UNDER THE 3000 FT CLOUD COVER; I DID NOT SEE THE OTHER ACFT. I CALLED BASE FOR RWY 3; THEN FINAL FOR RWY 3; AND LANDED. AS I WAS WAITING AT THE APCH END OF RWY 3 FOR ANOTHER DEP; I AGAIN HEARD CESSNA. THIS TIME HE SAID '4 MI STRAIGHT-IN FOR RWY 3.' I COULD SEE AN ACFT ABOUT IN THE POS OF THE CALLER AND DETERMINED I HAD PLENTY OF TIME TO SAFELY DEPART. I CALLED MY DEP; 'CLOSED PATTERN;' AND DEPARTED. AT ABOUT 400 FT AGL I OBSERVED AN ACFT; WITHOUT LNDG LIGHTS; ON ABOUT A 1 1/2 - 2 MI FINAL APCH FOR RWY 21; THE OPPOSITE RWY! I WAS ABLE TO START A R XWIND IMMEDIATELY (R TFC) AND CALLED IT ALSO FOR THE BENEFIT OF THE APCHING ACFT. THE APCHING ACFT MADE AN INITIAL TURN TO THE R; THEN TURNED TO THE L; AND THEN CALLED HE WOULD FOLLOW ME FOR RWY 3. THE OTHER ACFT APPEARED TO BE A C150; WHO EXECUTED A TOUCH-AND-GO AND DEPARTED THE AREA. THE ACFT I THOUGHT WAS ON FINAL TURNED OUT TO BE ANOTHER ACFT MERELY TRANSITIONING THE AREA; COINCIDENTALLY ON THE FINAL COURSE FOR RWY 3. THE UNICOM OPERATOR SAID HE SAW THE INCIDENT AND CONFIRMED MY UNDERSTANDING THAT THE PLT HAD CALLED A 4+ MI STRAIGHT-IN FOR RWY 3. ALTHOUGH THERE WAS NEVER LESS THAN A 1 - 1 1/2 MI SEPARATION; THERE OBVIOUSLY EXISTED THE POTENTIAL FOR A SERIOUS ACCIDENT. SEVERAL OBSERVATIONS COULD BE MADE ABOUT THE INCIDENT. NIGHT OPS INCREASE GREATLY THE NEED FOR INCREASED VIGILANCE FOR ALL PLTS; ESPECIALLY IN AREAS WHERE MANY LIGHTS THAT MAKE IT DIFFICULT TO SEE OTHER LOW ALT ACFT. ADHERENCE TO RECOMMENDED PROCS; INCLUDING TFC PATTERNS; COMMUNICATING WITH THE LCL UNICOM (WHICH WAS ON DUTY THAT NIGHT); REDUCE THE LIKELIHOOD OF CONFLICTS; AND REDUCE THE LIKELIHOOD OF ACCIDENTALLY USING A RECIPROCAL RWY. LASTLY; I COULD HAVE DELAYED MY DEP UNTIL I CONFIRMED I HAD THE ACTUAL LNDG ACFT IN SIGHT. IT IS PROBABLE THAT HAD AN ACCIDENT OCCURRED; THE FAULT WOULD HAVE BEEN WITH ME; THE DEPARTING ACFT; SINCE LNDG ACFT HAVE THE RIGHT- OF-WAY; EVEN IF THEY LAND ON A DIFFERENT RWY THAN THEY ANNOUNCE.