* start the detrend verify run:
  dettool -dbname gpc1 -definebyquery -mode verify -det_type FLAT_RAW -workdir neb://@HOST@.0/gpc1/detrend.200809 
    -inst GPC1 -filter r -select_filter r.00000 -select_dateobs_begin  2008-09-05 -select_dateobs_end 2008-09-06 -select_exp_type skyflat

 * examine the residuals and exclude obviously bad images:
  dettool -dbname gpc1 -updateresidexp -det_id 19 -iteration 0 -reject -exp_id 20206