Astrophotography With A Reducer - 2

Following on from my successful day-time focusing experiment using a 0.5x focal reducer on my Meade LX-90, I tried using the reducer on the telescope at night.

My first test object (after focusing with a Bahtinov mask) was Omega Centauri and the result was somewhat disappointing, with nasty flaring around the outer edges. This single exposure was twenty seconds at ISO 4000 on my Canon EOS 60D:

I was using a light pollution reduction filter that night, mounted inside the camera. The image was reasonably well focused but those flares wreck the image!

Here is a similar image (10 sconds, ISO6400) I took the next night but without the LPR filter:

So it wasn't the filter. 

The following image (of the Eta Carina Nebula!) was of 25 seconds duration at ISO 6400 with the LPR. You can't see the nebula for all the flaring!

So I got the same flaring two nights running and also on more than one object. 

The telescope equipment was: LX-90 with 2" SCT adaptor.

The Camera equipment was: Canon 60D, EOS T-Ring, 42-48 step ring and focal reducer (without the loose T2-Adaptor) as per the bottom of my previous post:

I asked my friends at Macarthur Astronomical Society and it was suggested that it is likely due to an off-axis optical component. 

The issue is not noticeable when I use the telescope without the 0.5 reducer, although obviously the field is much smaller. Here is the much better final image of Omega Centauti, taken without the reducer and without the LPR filter (3x30 sec, ISO 6400): 

So the finger seems to point at either (a) the focal reducer being off-axis or (b) the LX-90 mirror being slightly out of collimation (but not noticable without the reducer).