Initial number of stars found were 85 with the blue filter and 82 with the green filter.

After deleting the stars that lied in the edges of the frame, B: 79 stars, V: 76 stars.

Plotted the stars in the blue and the green in the same plot to see their offset

Then calculated the offset for the brightest star and defined the delta x and delta y. moved each star in the blue frame by that delta x and delta y.

However, the stars did not match, except for the brigthest one, because the baricenters in B and V are calculated depending on the pixel values of the star. This means that the same star taken with the B filter could be 'bigger' than in the V filter. This causes an offset in the barycenter calculation between the two filters.

Separation histogram was made after the offset calculation for the brightest star and for a random one, identified in the plot above. (Ignore light blue cross.)

After matching the stars barycenters, this were the results obtained.

First HR diagram, only 19 stars have been matched. Have to work further on the algorithm that matches stars.

compare with diagram found online: