As is generally known, the GSO RC telescope series suffers from having too short a 1ary baffle.  This admit light rays from outside the field-of-view, causing large and wide faint arcs in field, with a radius of curvature comfortable larger than the sensor size.   They are ugly, and (at least for me) impossible to remove in post.

However, there is a straightfiorward fix by adding an extension [or replacing) to the 1ary baffle making it longer and preventing off-axis rays from entering.  Or so I thought.

I have been using my GCO RC12 for over 12 months with an "add on" baffle which removed the problem.  However, a week ago I swapped my Optolong LRGB filters for an Antlia set and the ghosts have returned with a vengeance, even though this is the only thing I have changed in the optical train.

It have checked that I didn't leave off the extension to  1ary mirror baffle [not impossible for me to do!] and tried with a number of flat fields (no difference) and different telescope pointings.  As expected for scattered stray light, it is worst in B and L and varies in position from field-to-field.  

The simples thing for me to do would be to revert to the Optolong filters, but I would like to know why a simple filter upgrade(?) could result in such a big difference.  

Has anyone else had a similar experience?  Could it be that the Antlia filters all have bigger blue leaks, or more stray reflections from front surface?  I find all of this had to find credible, and I know that trying to track down stray light issues can be an exercise in futility, but if anyone has had a similar experience, it would reassure me that I am not going mad.

Thanks in advance Brian
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