[click on image to see a larger one]
Visible light image (400-750nm):

Reflected UV image using Baader-U filter (320-395nm):

Diptych of visible image (left) and reflected UV image (right):

In visible light, all flowers are rather bright to our human eye. But this R. hirta flower in UV (only visible to bees and butterflies) shows a very prominent and bright bullseye pattern, as its petals are very UV bright (around 365nm) and its center is very UV dark, compared to the rather dull UV reflecting Monardia and Echinacea flowers (around 380nm only), hence creating an impressive competitive edge in terms of chances for getting pollinated - and all this gets nicely visible.
Stay tuned, more will follow on that fascinating subject...