Hi Cristian,
Thanks for the reply. I have to confess to trying some parabolisation strokes on the mirror before taking these photos, and I guess that this is not what you are recommending. Just to confirm - you recommend going back to a spherical surface, then parabolising from there with a single type of stroke in order to get that best figure on the mirror. Also, my tester is not showing more than about 3 bands outside the ROC. Is this normal, or should I try inceasing the slit size or some other remedy. I have to admit this mirror figuring is turning out to appear a bit like sorcery to me.
Regards.
David.