SCT External Focuser: Real Difference or Total Overkill?

SCT external focuser vs internal focuser: I tested the PrimaLuceLab ESATTO 2" LP against the SESTO SENSO 3-SC on a Celestron EdgeHD 8 using NINA autofocus data. Many Schmidt-Cassegrains and Maksutovs focus by moving the primary mirror. This can cause image shift, focus shift, less repeatable autofocus curves, and occasional outlier runs. An external focuser like the ESATTO moves the imaging train instead, while an internal motor like the SESTO SENSO 3 still drives the telescope’s native focuser. In this video, I compare both systems on the same EdgeHD 8, alternating autofocus runs through the night to test final HFR, autofocus reliability, image shift, fit quality, and consistency. The result: both focusers work, but the ESATTO produced better average HFR, no visible image shift during focusing, and fewer questionable autofocus results. Resources (affiliate links): PrimaLuceLab ESATTO 2” Low Profile Focuser: US Link: https://bit.ly/4nqMqVJ EU Link: https://bit.ly/SESTOSENSO_EU UK link: https://bit.ly/ESATTO_UK PrimaLuceLab SESTOSENSO 3-SC Focus Motor: US Link: https://bit.ly/4wm4X9S EU Link: https://bit.ly/ESATTO_EU UK link: https://bit.ly/SESTOSENSO_UK Sesto Senso 3-SC Test&Review:    • Focusing with my Sixth Sense - PrimaLuce S...   Clear skies, Luca Chapters: 00:00 Introduction 00:32 The problem with the stock focuser 01:37 External focusers 01:59 Previous testing of the Sesto Senso 02:50 The Double Focuser SCT 03:56 Tech Specs of the 2 Focusers 05:00 Installation of ESATTO LP 2" 06:22 Testing Results: Image Shift 07:36 Results: Autofocus Performance 15:50 External Vs Internal Focuser - Tradeoffs 17:53 Conclusion #astrophotography #SCT #PrimaLuceLab #ESATTO #SESTOSENSO #NINA #telescope #autofocus