PLT OF A C172 OBSERVED SKYDIVERS FALLING APPROX 2000 FT AWAY FROM HIS ACFT AFTER BEING ADVISED BY ATC TO ALTER COURSE AROUND AN UNCTLED ARPT OVER WHICH PARACHUTE JUMPERS WERE GOING TO JUMP. PLT HAS GOOD SUGGESTION FOR DISSEMINATING PURPOSED SKYDIVING ACTIVITY.

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WE WERE CRUISING SE ON A COURSE THAT WOULD TAKE US DIRECTLY OVER THE BYRON ARPT. AT 3 NM NW; WITH THE ARPT IN SIGHT (THROUGH A SCATTERED LAYER 2000 FT BELOW); THE APCH CTLR SUGGESTED A TURN TO PASS EITHER E OR W OF THE ARPT BECAUSE OF AN IMMINENT SKYDIVING DROP. WE ALTERED COURSE SLIGHTLY TO THE S TO PASS W; WHICH HAPPENED TO BE UPWIND OF THE ARPT. MOMENTS LATER; WE OBSERVED FREEFALLING SKYDIVERS AT 2 O'CLOCK AND 11 O'CLOCK POS AND CLOSE RANGE. WE WERE GIVEN A FREQ CHANGE MOMENTS AFTER SIGHTING THE JUMPERS; AND ON THIS FREQ THE STOCKTON APCH CTLR WAS ASKING IF THE SKYDIVING AIRPLANE HAD RELEASED ITS JUMPERS YET. OUR EVASIVE ACTION AFTER BEING TOLD OF THE JUMP WAS OBVIOUSLY INADEQUATE. WE PASSED W OF THE AIRFIELD; BUT BY ONLY ENOUGH MARGIN TO FIND THE SKYDIVERS. BY THE TIME WE RECEIVED THE ADVISORY WE SHOULD HAVE MADE A MUCH LARGER TURN TO AVOID THE HAZARD; BUT GIVEN OUR PROX; THE WARNING SEEMED VERY LATE. THERE WAS CONFUSION BTWN THE CTLRS AND JUMP ACFT AS TO WHAT WAS HAPPENING; AND THE LOCATION OF THE SECTOR BOUNDARY SO CLOSE TO THE JUMP AREA PREVENTS NON PARTICIPATING AIRPLANES FROM OVERHEARING THE ACTIVITY AS THEY APCH FROM THE NW. EDUCATION IS A DEFINITE SOLUTION. THE AIM OFFERS LITTLE ADVICE; BUT 3 NM MINIMUM DISTANCE FROM PARACHUTE OPS SOUNDS LIKE A GOOD MARGIN; ALSO FOR PEOPLE NOT TO JUMP WITH ACFT BELOW. WE FREQUENTLY HEAR JUMPING ANNOUNCEMENTS ON CTAF FREQS; BUT NOT OFTEN THE ESTIMATED DURATION OF THE JUMP ACTIVITY THAT THE AIM SUGGESTS BE PROVIDED. MORE DETAILED INFO IN THE AIM MAY LEAD TO BETTER PLT UNDERSTANDING OF PARACHUTING EVENTS AND FEWER CLOSE CALLS. I HAVE SINCE REVIEWED FAR 105. 105.25 ALSO MENTIONS DURATION OF JUMP; RADIUS OF JUMP ZONE AROUND TARGET. THESE DETAILS SHOULD ALWAYS BE PROVIDED TO NON PARTICIPANTS.