NIGHT VFR XCOUNTRY TRAINING FLT INADVERTENTLY MAKES APCH TO LAND AT A MIL BASE INSTEAD OF NEARBY CIVIL ARPT.

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WHILE FLYING ON A NIGHT VFR XCOUNTRY FLT RETURNING TO MYF ARPT FROM SNA; I WAS INSTRUCTING MY STUDENT. WE WERE IN CONTACT WITH SOCAL APCH WHILE AT 5500 FT MSL AND GIVEN A CLASS B CLRNC ON V23 DIRECT MZB VOR. AS WE APCHED OCEANSIDE VOR; WE WERE ENCOUNTERING A CLOUD LAYER BASED AT 3000 FT AND TOP AT 4000 FT JUST ALONG THE COAST LINE THAT WAS STARTING TO MOVE INLAND AS A SCATTERED CONDITION. APCH OK'ED US TO DSND DOWN TO 3500 FT. I FELT THAT WOULD PUT US TOO CLOSE OR INTO THE CLOUDS; SO TO STAY VFR I ADVISED SOCAL WE WOULD STAY AT 5500 FT UNTIL CLOSER TO MZB. AS WE SAW THE CLOUDS BREAKING; WE THEN DSNDED TO 3500 FT OVER MOUNT SOLEDAD. I SHOULD HAVE HAD MY STUDENT CONTINUE DIRECT TO THE VOR; BUT INSTEAD WE THOUGHT WE WOULD CONTINUE THE DSCNT AND GO DIRECT TO MYF ARPT. THE OTHER MISTAKE WAS WHEN SOCAL ASKED IF HE COULD ASSIST US ANY MORE; WE SAID WE COULD HANDLE IT. ON LOOKING BACK; WE SHOULD HAVE ASKED FOR RADAR VECTOR TO MYF. AT NIGHT; THE FAMILIAR LANDMARKS SUDDENLY LOOKED DIFFERENT. WHEN WE TURNED OUR C172 TOWARD MYF; WE THOUGHT INSTEAD WE WERE UNKNOWINGLY HDG TO THE MIRAMAR MARINE STATION; WHICH IS LOCATED FAIRLY CLOSE TO MYF WITHIN 10 MI TO THE N AND HAS 2 E/W RWYS LIKE MYF. WE CONTINUED HEADING TOWARDS MIRAMAR THINKING IT WAS MYF; AND ALSO WERE CALLING IN ON THE MYF ARPT FREQ OF 119.2 SINCE THE TWR WAS CLOSED. AS WE GOT CLOSER; I THOUGHT IT STRANGE THE ARPT LOOKED DIFFERENT BUT THE RWYS STILL WERE IN THE SAME DIRECTION I EXPECTED. ALSO; I THOUGHT IT STRANGE THAT MY KEYING THE MIKE HAD NO EFFECT ON THE RWY LIGHT INTENSITY. WHEN WE TURNED FINAL I REALIZED THIS RWY WAS NOT THE RWY 28L AT MYF AND IMMEDIATELY INSTRUCTED MY STUDENT TO DO A L CLBING TURN AND DEPART TO THE S TO MYF. WE DID LAND SAFELY AT MYF AND I WAS INSTRUCTED BY A POLICE HELI OVERHEAD TO PHONE MIRAMAR TWR REGARDING THIS ARPT INCURSION. I APOLOGIZED TELLING THEM I GOT THE ARPT MIXED UP. THEY JUST WANTED ME TO GET MY NAME AND ACFT NUMBER AND SAID THERE WOULD BE NO ACTION TAKEN. IN LOOKING BACK ON THIS; ALL THIS COULD HAVE BEEN PREVENTED IF I WOULD HAVE JUST FOLLOWED THE 145 DEG RADIAL TO MZB VOR AND THEN TURNED NE TO TRACK THE 055 DEG RADIAL TO MYF. ALSO; I COULD HAVE STAYED WITH SOCAL APCH WHO WOULD HAVE GIVEN ME VECTORS TO MYF.