Joe, I'm not sure if you are now talking about H-a filtration or long-pass filtration. And, without knowing which type of filter, I can't answer your question.
A thought I had: for slower optics like f2.8, how would rear vs front mounted compare in terms of contrast and eof?
I don't consider f:2.8 a slow optic. My test photos in post 1&2 speak for themselves regarding H-a filtration. And as noted, I also tested my f:2.8 Newt with the filters mentioned with almost identical results compared to the camera lenses.
As Butterfly explained, long-pass filters are very different; they do not present the same challenges as narrow band-pass H-a filters. Long-pass filters can prevent the aspect of star bloat that derives from chromatic distortion. For example, a 640nm long-pass can eliminate most chromatic distortion when used with NV in my 120mm f:5 achromat, because it is blocking most of the shorter, visible wavelengths... which is why they are used as light pollution blocking filters with NV.
Edited by GeezerGazer, 08 July 2021 - 02:21 PM.