Back-Focus 101: How Filters Affect Back-Focus
14:34
Back-Focus 101: Celestron 8" EdgeHD SCT (no reducer)
18:45
Telescope Back Focus: The Ultimate Guide [TAIC Short]
11:32
Back Focus Explained - Astrophotography
23:44
What is BACKFOCUS?? And how to deal with it? - Starting Astrophoto for Lazy People - Ep 8
11:53
Back-Focus 101: The Petzval Lens ft. William Optics RedCat51
17:30
Triplet Refractor Apo Reducer/ Flattener - Attachment & Backfocus
8:10
Backfocus with an ZWO Cooled Camera
8:37