COMPASS PROB CAUSES COURSE DEV.

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ON DEP FROM BDL 5 DEP RWY 6; WE WERE GIVEN A FEW VECTORS AND THEN INSTRUCTED TO PROCEED DIRECT TO CTR. THE FO; WHO WAS THE PF; TURNED TOWARD THE VOR AND APPEARED TO BE TRACKING DIRECTLY TO IT. I THEN PULLED OUT MY CHART AND TUNED OUR NEXT FIX; CAM. I THEN NOTICED THE FO WAS 1 DOT L OF COURSE AND TURNING TO TRACK DIRECTLY TO CTR. AT THIS TIME THE COMPASS DEV LIGHT ILLUMINATED; INDICATING A DIFFERENCE BTWN OUR 2 HEADINGS. AFTER 10 SECONDS OF COURSE CORRECTION AND VERIFICATION WITH OUR STANDARD COMPASS; WE REALIZED WE WERE ABOUT TO PASS SLIGHTLY W OF CTR. AT THE TIME I WAS CONSIDERING A SHARP EVASIVE MANEUVER TO TURN AND CROSS DIRECTLY OVER THE VOR (CTR). I AM SURE THIS WOULD HAVE CAUSED AN OVERSHOOT ON THE OTHER SIDE OF THE VOR. GIVEN OUR ALT AND COURSE DIRECTION; I DIDN'T THINK WE WOULD VIOLATE ANY AIRSPACE BY XING SLIGHTLY W OF CTR. ATC ASKED IF WE WERE PROCEEDING DIRECTLY TO CAM; WE ADVISED; AFFIRMATIVE SINCE OUR COURSE PASSING W OF CTR WAS NOW DIRECT CAM. HE THEN ADVISED US THAT WE WERE XING CTR 3 MI L OF COURSE. I DON'T KNOW WHETHER WE VIOLATED ANY AIRSPACE OR NOT. IN RETROSPECT I SHOULD HAVE ADVISED ATC IMMEDIATELY OF OUR COMPASS PROB AND ASKED IF HE HAD ANY PROBS WITH OUR COURSE.