Hello,
In order to see the edge image, I simply call the cv.Canny function with the same parameters I pass to the cv.HoughCircles (the lower threshold is higher_threshold/2):
edges = cv.Canny(my_image, 50, 100)
cv.imwrite('Edges_my_image', edges) #save image into file
For what the accumulator matrix is concerned, someone has any hints on how to visualize it?