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No I don't have that scope or FF. I did have a TEC110 F5.6 fluorite triplet with a TEC field flattener that had no issues. But I have seen bright out of view flares from bright stars and reflections from flatteners.
I have even had a reflection issue on an AP quad TCC flattener/reducer which was very expensive. In that case it was my adapter which had a step down inside it and that step caused a reflection artifact. Nothing as bad as your example but it looked like a spiral galaxy in the view which of course wasn't real.
Anodised aluminium does reflect in IR.
Flatteners with poor antireflection coatings will bounce light back and forth from the sensor or filters off the rear flattener element.
This is why Tak and AP and other high end flatteners and reducers cost so much. They need the good glass and the high end coatings to get a good result.
Roland Christen has posted in the past just how much coatings have advanced in the last several years.
Alnitak (from the Horsehead region) is the ultimate torture test for reflections so the fact its horrendous here is the worst it will get.
Try cutting a donut shaped disk out of some black non reflective thin cardboard and stop down your flattener a bit. Put it at the back or the front of the flattener wherever you can mount it and see what happens.
Probably the scope side of the flattener may be the best spot.
Greg.
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