Autofocus Challenges with an SCT

Mo' focal length, mo' problems. I'm using my Celestron C9.25 SCT (focal length - 2280 mm) with the NINA autofocus routine. So far, not so good. I've had great results with my refractors, but very poor results with the SCT. We take a look at NINA's Half-Flux Radius (HFR) and compare it to Astrophotography Tool's (APT's) Half-Flux Diameter (HFD) and Inverse Power method. APT's HFD wins! Will try the Hocus Focus NINA plugin next. APT Inverse Power Paper: https://drive.google.com/file/d/1LSuS... Bahtinov Mask Focuser Characterization:    • First Use of the Celestron Focuser on my SCT      • Introducing the William Optics GT81iv Refr...