I had a 36mm LRGBHOS (3nm) Chroma filterset to play with a couple days ago. I usualy focus using the L-Filter with and the Autofocus with NINA and recheck with a Batinov just in case.
Once focused the RGB filters where perfectly in focus but the Ha filter showed donuts on my f/4 Newtonian, forcing me to refocus.
Did anybody else experience this with faster scopes, I can't find any informations on the Chroma webpage as to if they guarantee homofocal filters.?