diff --git a/exp/board_detect.py b/exp/board_detect.py
--- a/exp/board_detect.py
+++ b/exp/board_detect.py
@@ -56,9 +56,9 @@ def filterStones(contours,bwImg,stoneDim
 		coverage1=area/(w*h or 1)
 		hull=cv.convexHull(c)
 		coverage2=area/(cv.contourArea(hull) or 1)
-		if coverage2<0.8:
-			cv.drawMarker(contourImg,tuple(map(int,center)),(0,127,255),cv.MARKER_DIAMOND,12)
-			keep=False
+		# if coverage2<0.8:
+		# 	cv.drawMarker(contourImg,tuple(map(int,center)),(0,127,255),cv.MARKER_DIAMOND,12)
+		# 	keep=False
 		if keep:
 			res.append((EPoint(*center),c))
 			cv.drawMarker(contourImg,tuple(map(int,center)),(255,0,0),cv.MARKER_CROSS)
@@ -117,14 +117,12 @@ class BoardDetector:
 		# detect lines from edges and stones
 		edgeImg=prepareEdgeImg(rect)
 		hough=HoughTransform(edgeImg)
-		hough.extract()
 		stonesImg=np.zeros((self._rectH,self._rectW),np.uint8)
 		for (point,c) in stones:
 			cv.circle(stonesImg,(int(point.x),int(point.y)),2,255,-1)
 		# cv.drawContours(stonesImg,[c for (point,c) in stones],-1,255,-1)
 		show(stonesImg,"detected stones")
-		# hough.update(stonesImg,5)
-		hough=HoughTransform(stonesImg)
+		hough.update(stonesImg,5)
 		hough.extract()
 
 		# # detect lines passing through the stones
diff --git a/exp/hough.py b/exp/hough.py
--- a/exp/hough.py
+++ b/exp/hough.py
@@ -27,7 +27,8 @@ class HoughTransform:
 
 	def extract(self):
 		shift=self._diagLen//2
-		peaks=sorted(list(findPeaks(self._acc)),key=lambda rc: self._acc[rc],reverse=True)[:2*19]
+		allPeaks=sorted(list(findPeaks(self._acc)),key=lambda rc: self._acc[rc],reverse=True)
+		peaks=allPeaks[:38]
 		peaks=[(alpha,d-shift) for (alpha,d) in peaks]
 		peaks=self._filterClose(peaks)
 		peaks.sort(key=lambda rc: rc[0])
@@ -35,6 +36,7 @@ class HoughTransform:
 		(alpha,beta)=self._detectDominantAngles(peaks)
 
 		img=self._createImg()
+		img=self._markPeaks(img,self._filterClose(allPeaks[:38]))
 		doublePeaks=peaks+[(alpha+180,-d) for (alpha,d) in peaks]
 		params=self._computeGridParams([(gamma,d+shift) for (gamma,d) in doublePeaks if alpha<=gamma<=alpha+self._angleBandwidth])
 		self._drawGridCurve(img,params,0)
@@ -63,7 +65,7 @@ class HoughTransform:
 		"""Discard points with Euclidean distance on the original image lower than 10.
 		From such pairs keep only the one with a higher value in the accumulator.
 		This can delete a series of points. If a-b and b-c are close and a>b>c, only a is kept."""
-		minDist=10
+		minDist=13
 		center=EPoint(*self._center)
 		res=[]
 		for (alphaDeg,d) in peaks:
@@ -93,7 +95,7 @@ class HoughTransform:
 		log.debug("angles histogram: %s",histogram)
 		dominantAngles=sorted(histogram,key=lambda xy: xy[1],reverse=True)
 		alpha=dominantAngles[0]
-		dominantAngles=[beta for beta in dominantAngles if 165>abs(alpha[0]-beta[0])>15]
+		dominantAngles=[beta for beta in dominantAngles if 180-bandwidth>abs(alpha[0]-beta[0])>bandwidth]
 		beta=dominantAngles[0]
 		log.debug("dominant angles: %s, %s",alpha,beta)
 		return (alpha[0],beta[0])
@@ -126,6 +128,12 @@ class HoughTransform:
 
 		return img
 
+	def _markPeaks(self,img,peaks):
+		colors=[[255,0,0],[255,255,0],[0,255,0],[0,255,255],[0,0,255]]
+		for (i,(alpha,d)) in enumerate(peaks[:38]):
+			cv.drawMarker(img,(d,alpha),colors[i//9],cv.MARKER_TILTED_CROSS)
+		return img
+
 	def _drawGridCurve(self,img,params,colorKey=0):
 		colors=[[0,255,255],[255,0,255],[255,255,0]]
 		color=colors[colorKey]