APT User Guide - Focusing Aid

Astro Photography Tool Video User Guide Focusing Aid Focusing Aid allows achieving near perfect focus using the HFD (Half Flux Diameter) and/or FWHM (Full Width Half Maximum) metrics to measure the focus quality. The lowest value is the best one. It is advisable to rely on HFD instead of FWHM, because the first is more stable against the atmosphere turbulence. HFD works with the whole star area while FWHM works only with the line of the star profile. Thankfully some semi-clear skies allowed me to get in & do this under live conditions which is needed to demonstrate Focusing Aid fully. Online written guide - Focusing Aid https://www.astrophotography.app/usersguide/focusing_aid.htm APT Links Homepage: https://astrophotography.app/ Forums: https://aptforum.com/phpbb/ User Guide: https://www.astrophotography.app/usersguide/ Support APT! Having alternatives drives progress! https://astrophotography.app/alternatives.php Ivo Stoynov (APT creator) "Focusing A to Z" talk on The Astro Imaging Channel: https://www.youtube.com/watch?v=OzvZCvz0t4Q The Astro Imaging Channel: https://www.youtube.com/@TAIC