Arrays of Franck-Condon factors (qνprimeν−or+) and r centroids (rνprimeν−or+), which are closely related to relative vibrational transition probabilities, have been computed upon a Morse model for the B - X and C - X systems of the MgF molecule. This molecule is of importance to astrophysicists as it occurs in the spectra of sunspots. The r centroids for a given (νprime, ν−or+) band have been found to decrease smoothly with increase of corresponding wavelength λνprimeν−or+. The value of Δr identical with rνprime + 1,ν−or+ + 1 -rνprimeν−or+ in a sequence has also been found to remain constant. The computed values of the r centroids indicate that the potentials are neither very anharmonic nor very wide.