i've recently acquired from CN classified a WO BV set which included the WO 1.6 barlow nose piece.
i've used it with two scopes (C8 EDGEHD and an AT102ED) with a stock 1.25 prism diagonal that came with the C8.
no problems achieving focus on the C8, but the AT102ED is more challenging.
with the 1.6 attached to the nose of the BV, most of the time i can achieve focus
before the focus bumps up against it's most inward travel.
yesterday in the daylight i took the time to 'dial' in the diopter of both eyepieces by focusing on top of a radio tower about 3 or 4 miles away.
last night, i couldn't get infinity focus even at the most inward focuser position and rotating the eyepiece diopters to either limit.
in frustation, i moved the 1.6 barlow in front of the celestron diagonal instead of after.
with that change, i achieved infinity focus and seem to have much more latitude in focuser position.
what am i giving up by moving the barlow forward of the diagonal?
is the effective FL of the AT102ED different with the barlow forward instead of aft of the diagonal?