NMAC BTWN A CHRISTEN EAGLE TURNING FROM BASE LEG ON FINAL AND A HOT AIR BALLOON DSNDING WITHIN 1 MI OFF THE ACTIVE RWY THRESHOLD.

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WHILE IN A LCL PRACTICE AREA W OF BOLTON FIELD; I OVERHEAD BOLTON TWR CLRING A BALLOON FOR LAUNCH OR LIFTOFF (I FORGET EXACT WORDING). BALLOON PLT MADE COMMENT THAT HE'D BE 'OPERATING NW OF ARPT.' TWR RESPONDED 'OPERATE AT OWN RISK.' SHORTLY THEREAFTER; TWR BROADCAST CLOSING DOWN ANNOUNCEMENT (XA30 LCL); ADVISORY FREQ 128.1 (SAME AS TWR OPERATING FREQ). THE ACTIVE RWY HAD BEEN RWY 22; WITH SEVERAL ACFT LNDG THERE PRIOR TO TWR CLOSURE. I MADE INITIAL CALL INBOUND (1 MI N OF SMALL TOWN) FOR FULL STOP. CLOSER IN; I OBSERVED 2 BALLOONS JUST TO NW OF APCH END OF RWY 22 AT ESTIMATED 800 FT AGL. I ENTERED UPWIND 22 MI SW OF THEIR POS; AND CALLED UPWIND AND THEN DOWNWIND (L PATTERN). I MOMENTARILY CONSIDERED USING RWY 4; BUT REJECTED DUE TO CONCERN OF POTENTIAL HEAD-ON WITH ACFT (RAMP IS VERY CLOSE TO APCH END RWY 22) AND VISIBILITY POOR. AT NO TIME AFTER THEIR INITIAL CONTACT WITH TWR EARLIER DID I HEAR ANY COM FROM BALLOON. UPON TURNING BASE TO RWY 22; I OBSERVED ONE OF THE BALLOONS SEEMED LOWER THAN BEFORE RELATIVE TO OTHER; AND HAD DRIFTED CLOSER TO EXTENDED RWY CTRLINE. I CUT AN ANGLING BASE TO FINAL TURN EARLIER THAN I ORIGINALLY INTENDED; WHICH WAS EXTENT OF 'EVASIVE MANEUVER.' HIGHER THAN NORMAL APCH; NO SWEAT IN BI-PLANE. UPON TAXI BACK FROM LNDG; I NOTICED BALLOON TOUCHING DOWN 3/4 MI NE OF THRESHOLD RWY 22 IN OPEN FIELD ON EXTENDED CTRLINE. THERE WAS NEVER ANY COLLISION DANGER AS BALLOON NEVER REMAINED STATIONARY IN VIEW; AND ORIGINAL BASE TURN WAS EVEN; OR SLIGHTLY INSIDE BALLOON PATH. I DON'T KNOW IF MY PRESENCE IN PATTERN CAUSED BALLOON TO ADJUST HIS FLT PATH; OR NOT; OR IF HE WERE CONCERNED ABOUT SEPARATION. HOW DO YOU 'CUT OUT' A BALLOON WHEN BOTH OUR LNDG SITES ARE SLIGHTLY DIFFERENT? SOME FACTORS: 1) RECENT LIFTOFF (IT MAY HAVE BEEN 'OTHER' BALLOON) LED ME TO EXPECT THAT BALLOON WOULD BE SLOWLY DEPARTING AREA. 2) IF BALLOON HAD COMMUNICATED INTENTION OF LNDG NEAR APCH END; I; RWY 22; WOULD HAVE LANDED ON RWY 4 (WIND WAS LIGHT); INSTEAD. 3) CTL TWR CLOSING MAY HAVE INDUCED BALLOON PLTS TO SHUT OFF RADIO; NOT A GOOD THING WITH CTAF AVAILABLE. 4) IT REALLY IS DIFFICULT TO GAUGE JUST WHAT BALLOON IS DOING.