Dpierce54 If not, how can I use ASIAIR to determine the FWHM.
From my email conversations with them in the past, ZWO claims to use Half Flux Diameter (HFD).
As to how to get FWHM from HFD... HFD is equal to FWHM iff the star profile is Jointly Gaussian, which is a good approximation only when "seeing" bloats the star by a lot. When "seeing" is perfect, the star takes the profile of an Airy disk instead of a Gaussian -- HFD and FWHM deviates from one another as "seeing" gets better (i.e., as HFD becomes smaller). For intermediate values, the star profile is the Gaussian convolved with the Airy disk.
https://en.wikipedia.org/wiki/Half_flux_diameter
If you really need FWHM from ASIAIR, you can download an image and compute it.
https://en.wikipedia.org/wiki/Full_width_at_half_maximum
Chen
