I have just started using ThunderSTORM and was curious as what to set the initial sigma value for the PSF localization options. The default is 1.6 px and I read in a manual that this is due to the Abbe limit of diffraction. If this is true, would using a different microscope with different wavelengths of light and numerical apertures require specific initial sigma values based on the new Abbe limit? The manual also says that the fitting radius should be an integer around 3 times the sigma value but I am unsure as to what the explanation for that is. If anyone could help me with this that would be greatly appreciated.