Field flattener question

[MishMich]

There was a discussion here recently about focal reducers and field flatteners. Nobody could say for sure whether a 0.8 FR would work with my Onyx or not, and the sense I got was 'try it and see'. So, as I don't actually need a wider field of view for the Onyx, I got a Revelation FF - which the blurb says is ideal for refractors up to f/6, and will work with fracs either side of that (I forget the lower level, as it doesn't apply to me). The Onyx is f/6.3, and is much the same as the Equinox, which I beleive the SW FF is supposed to work with.

So, I hook it up, placing the LPR in the FR, and what I get is not good. I get what looks like coma - but on the LHS of the image, not the RHS. The flattener certainly has an effect, because the stars a positioned slightly differently. It is not down to guiding, because on the LHS they trail to the left, top LHS they are at about 30 degrees from horizontal, and bottom LHS they trail -30 degrees. But not on the right. So, I have a FF that doesn't seem to work with my scope. But I am puzzled as to why I get the effect on one side and not the other. I guess the weight of the camera may have pulled the tube slightly out of centre, although I am sure it was mounted horizoontally. I was shooting Pleiades, and found on other shots of Orion that the RHS showed more vignetting, which I initially put down to the home-made dew-shield extension not being quite right, but I do use the DSLR aligned vertically for that shot, so maybe the weight is pulling the alignment out slightly along the tube somewhere.

I wondered if anybody has any ideas about this. If it is the weight of the camera pulling along the focuser tube assembly somewhere, how do I adjust for that? Would a poorly constructed dew shield account for both vignetting and this phenomenon (I don't recall seeing any vignetting with 2" fittings before the extra dew shield)? Might the FF be OK (given it works for the rest of the frame), but highlighting some other problem in the setup.

I suppose what I am more concerned about is whether this is highlighting something more serious, like the ED being out of collimation somehow. If that is the case, would it be fixable by me, or would I need to get back to the supplier to fix?

Or is the Revelation FF just rubbish, and should I see if I can get to return this and not bother with one?

With & without shots follow...

M.

[Magnum]

I know it sounds silly, but it almost looks like the before and after pics have got mixed up, are you sure you haven't made a mistake with the order.

[Coco]

Firstly you must take an image without the flattener and asses your scope is

1. the draw tube is central

2. the lens is collimated

A scope that need a flattener should have equally radiating out stars from the centre as am sure you already are aware.

Take the focus system off your main tube and make sure the focus draw tube is equally spaced between.

Check the gap that's coloured red: