Could't do anything about the weather for the moment, I decided to do a summary the barlow combinations with the Leica zoom, mainly with Baader VIP barlow parts, also baader 7.5mm spacing part 1508155. 1. Calculating barlow effect: 1 + (L_FP + added_length)/ VIP_fl where L_FP is Leica's focal plan position, it's 4.5mm inside the length (info from Andreas Braun) added_length is 2" dapter length plus addition adapter length, (the presentAPM 2"T2 adapter is 25mm for by my measurement. VIP_fl is VIP