[Shiraz (Ray)]

thanks very much Rick and many thanks to Richard as well.

the only thing I would add is that Richard's tutorial applies to diffraction limited stars and ignores atmospheric seeing. The star profiles presented earlier incorporate atmospheric seeing and that will be the primary determinant of resolution. However, the general point that the star size may be entirely explained by the optical physics of image formation is still appropriate. That includes the violet halos that occur when using a refractor that has been optimised for visual use.

My understanding is that a small amount of charge diffusion may occur in some BSI chips in the visible band, where there may not be any potential barrier to charge movement (it may not only be NIR that does this). However, the FSI chips that we use have potential barriers to prevent lateral charge diffusion. As Richard says, our star shapes do not depend on charge spreading over the surface of the detector.

His graph showing how the minimum detectable signal varies with read noise is also germane to the two threads currently going on the new low read noise CMOS chips.