PSF wings about piff HOT 2 OPEN

I suspect this will be best done via the composite model that we are considering for the optical + atm PSF model. There the full model will be the convolution of several components. I think PixelGrid x Airy would probably do a decent job at this with only a couple extra degrees of freedom over the full PixelGrid in the center.
I don't know that convolution is ideal. Possibly addition is better. But once the Convolution composite is working, I think it will be trivial to also do a Sum one. (You could even have an arbitrary hierarchy of nested composites of the different types if you were so inclined.)

from piff.

I was thinking of something simple (and additive), like a power circular power law that covers pixels beyond the PixelGrid and might be feasibly added as a single extra DOF for this model to keep it linear. [I think the large-R behavior of a typical ground-based PSF is dominated by scattering and doesn't look like the Airy tails.]

from piff.