COMMUTER ACFT DSNDS AND FLIES TOWARD WRONG ARPT. ENTERS ATA.

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WHILE ENRTE FROM BOS TO MHT LEVEL AT 5000 FT; I (THE CAPT AND PF) WAS FLYING IN VFR CONDITIONS. BOS APCH HAD JUST HANDED US OFF TO MHT APCH AND MY FO RPTED IN WITH THE CURRENT ATIS. WE WERE THEN TOLD THAT THE RWY HAD CHANGED FROM RWY 6 TO RWY 35. THE CTLR THEN ASKED US IF WE WOULD LIKE RWY 35. WE ANSWERED YES. I THEN TOLD MY FO THAT I HAD THE ARPT IN SIGHT AND TO INFORM MHT APCH THAT WE HAD THE ARPT. THE APCH CTLR THEN CLRED US FOR A VISUAL APCH. AT THE TIME IT APPEARED TO ME THAT WE WERE VERY HIGH SO I ASKED THE FO TO REQUEST A 360 DEG TURN TO LOSE ALT. THIS WAS APPROVED BY MHT APCH. I THEN DSNDED TO 1800 FT AND WAS SETTING UP FOR THE APCH WHEN MHT APCH INFORMED ME THAT I WAS ON A 8 MI L BASE FOR RWY 35. I THEN LOOKED UP TO VERIFY OUR POS ON THE LORAN. IT SHOWED US 9 MI S OF THE ARPT. I THEN REALIZED THAT THE ARPT I THOUGHT WAS MHT WAS REALLY NASHUA (BOIRE); NH. I THEN CLBED TO 2000 FT AND LOCATED MHT ARPT AND LANDED WITHOUT INCIDENT. THE FOLLOWING WERE PROBABLE CONTRIBUTING FACTORS TO THIS SIT: 1) THIS IS A 40 NM FLT. THE AVERAGE FLT TIME IS 15 MINS. THIS GIVES A CREW VERY LITTLE TIME TO COPY THE ATIS; CALL IN-RANGE BRIEF PAX; BRIEF THE APCH; PERFORM CHKLISTS AND COM WITH ATC. 2) THIS WAS MY FIRST TIME INTO MHT ARPT AT NIGHT AND I SHOULD HAVE BEEN MORE CAREFUL AND UTILIZED ALL AVAILABLE NAVAIDS. AT THIS TIME I STILL DO NOT KNOW IF I HAD ACTUALLY PENETRATED THE NASHUA ATA. I AM FILING THIS RPT ONLY AS A PRECAUTION.