I have a 7 position, 36 mm ZWO EFW with astrodon filters. The positional accuracy after filter rotation appears to be poor, screwing up flat calibration of all images (see attached jpgs, a representative pre-rotation flat and a post-rotation calibrated light).
The larger dust motes (on the filter) move between the flat and the light, which makes the calibration and image worthless. Smaller motes, likely on the sensor window closer to the focal plane do not move and are properly calibrated out.
The wheel does not appear to be binding in rotation (I saw the earlier post about binding with astrodon filters). What is the spec for repeatability/accuracy in positioning each filter -- the mechanism is not complicated so I'm not sure what could be wrong with mine. If the spec for accuracy is this low to begin with, the EFW is not very useful for serious imaging.
R. Morrison
