Reducer for a short focus (420mm) APO?

[Star101]

Recently, I bought a 2" Astrophysics 0.67 Reducer for another scope which got sent back. I kept the 0.67 reducer for sometime in the future. While waiting for the future I was playing with my TS65EQ 420mm f6.5 scope as ya do! I placed the reducer on the front of the ATIK 3 nosepiece and slid it into the scope then wondered if I could find focus. Well, blow me down, I did  And I was impressed I could now fit objects in the FOV that would have needed a mosaic before.

On closer inspection, I noticed the corners of the image were not that great compared to the perfect flat image of the TS65EQ without any additional optics. 

The TS65EQ already has a field flattener built in. 

My question is, are there any focal reducers out there for such a short focal length scope? The ones I can find are for SCT's not APO's.

Unprocessed Trunk.

 

Corner edge

 

Trunk from basic TS65EQ no crop.

 

Edited August 21, 2020 by Star101