FLC OF AN ACR TURBOPROP INADVERTENTLY LANDED AT THE WRONG ARPT AT NIGHT. IN ADDITION; DSNDED THROUGH CLASS C AIRSPACE WITHOUT CONTACTING THE CTLING APCH CTL.

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DEST WAS SAC ARPT; FO WAS THE PF AND WAS USING BOTH GPS AND VOR TO TRACK TO THE SACRAMENTO VORTAC. FO WAS PLANNING ON FLYING THE VOR RWY 2 APCH AND CIRCLE TO LAND ON RWY 20. AS WE WERE DSNDING; ZOA; WHO WAS GIVING US FLT FOLLOWING; ADVISED US TO TURN 30 DEGS R TO AVOID TFC DEPARTING RWY 20 AT SAC ARPT. AFTER WE WERE CLR OF THE TFC; ATC ADVISED US THAT THE ARPT WAS AT 1 O'CLOCK; 8 MI; WHICH MATCHED OUR GPS POS. AT THIS TIME THE FO TUNED IN 119.5 WHICH IS SAC CTAF AND CLICKED THE MIKE BUTTON 7 TIMES TO ACTIVATE THE PLT CTLED LIGHTING. AS HE DID THAT; I NOTICED THE RWY LIGHTS GO FULL BRIGHT AT AN ARPT AT OUR 1 O'CLOCK POS AND APPROX 8 MI. ALSO AT THIS TIME I HEARD AN ACFT RPT ON FINAL TO RWY 20 SAC ARPT. AT THIS TIME; I ALSO OBSERVED AN ACFT ON FINAL TO THE ARPT I WAS OBSERVING. BELIEVING I HAD SAC ARPT IN SIGHT; THE FO SET UP FOR A L DOWNWIND TO FOLLOW THE LNDG ACFT. DURING OUR DSCNT INTO THE PATTERN THE FO DID NOT LOSE ALT FAST ENOUGH (WE NEEDED TO BE BELOW 1600 FT) WE ENTERED SAC CLASS C AIRSPACE WITHOUT PERMISSION. DURING THE DOWNWIND I WAS LOOKING OVER THE BUILDINGS ON THE ARPT AND OBSERVED THAT THE GENERAL LAYOUT AND POS OF THE BUILDINGS WERE THE SAME AS SAC EXECUTIVE; CONVINCED THAT THIS WAS IN FACT SAC ARPT I ALLOWED THE FO TO CONTINUE THE APCH AND LNDG. IT WAS DURING THE LNDG ROLLOUT THAT I REALIZED THAT WE WERE AT THE WRONG ARPT. I CHKED THE GPS AND IT SHOWED SAC ARPT WAS 8 NM W ON A 298 DEG HDG. I CHKED OUR LOCATION AND FOUND OUT THAT WE HAD LANDED AT MATHER ARPT; WHICH WAS AN UNCTLED ARPT. WE TAXIED BACK AND DEPARTED THE 8 NM TO SAC ARPT WITHOUT FURTHER INCIDENT.