How to get the distance between the major and minor axes an ellipse?

I am trying to use opencv in python to detect the distance between the major and bottom axes of an ellipse in an image, so far I detect the centroid. Any ideas to get the axes of the ellipse?

Thanks a lot

import time
import sys

import cv2
import numpy as np
# Read image.
img = cv2.imread('./imagenes/junio100.bmp', cv2.IMREAD_COLOR)
# Convert to grayscale.
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
# Blur using 3 * 3 kernel.
gray_blurred = cv2.blur(gray, (3, 3))
# Apply Hough transform on the blurred image.
detected_circles = cv2.HoughCircles(gray_blurred, 
                   cv2.HOUGH_GRADIENT, 1, 20, param1 = 50,
               param2 = 30, minRadius = 1, maxRadius = 40)
# Draw circles that are detected.
if detected_circles is not None:
    # Convert the circle parameters a, b and r to integers.
    detected_circles = np.uint16(np.around(detected_circles))
    for pt in detected_circles[0, :]:
        a, b, r = pt[0], pt[1], pt[2]
        # Draw the circumference of the circle., (a, b), r, (0, 255, 0), 2)
        # Draw a small circle (of radius 1) to show the center., (a, b), 1, (0, 0, 255), 3)
        print ("axis x:",(pt[0]))
        print ("axis y:",(pt[1]))
        print ("Diameter:",(pt[2]))
        cv2.imshow("Detected Circle", img)

if you had contours, you could try to fit an ellipse