Mdopp

I came across this rather old thread when I was looking for more information on this reducer. Maybe other people find it useful so I would like to share my experience with the 0,77 reducer on an 150ED and a full frame camera (ZWO ASI 6200MM). Of course, there is noticeable vignetting. But this can be corrected nicely by applying flats. The stars in the outmost corners are somewhat elongated but not too much. There are no dark areas in any of the corners. All in all, I think the reducer works quite OK with a full frame camera. This may be because the first lens of the reducer is actually placed inside the telescope‘s tube much further to the front than the camera sensor or the normal 1x field flattener. I assume that at this position the field is actually larger and so the reducer can indeed provide a full frame image. I am attaching an image that was shot with this setup. I only cropped some 10 pixels around the edges to remove the effects of dithering. Otherwise, this is the entire full frame.