A very important issue when imaging but of late I've had some issues getting it right due to deteriorating eyesight, presently I use a Bahtinov mask in conjunction with my capture software focusing aid in EZCAP QT, however even following guidelines by picking a star of around mag 7 then using the mask to get the spikes split perfectly the software is still returned FWHM figures of around 20-30 even those this is binned 2x2 still that seems excessive am I doing something wrong or is the software just returning erroneous figures.
