Good eyes :-). As I mentioned in the original post, "Dark, no flats." This was a quick test of the Radian filter over a couple of nights at my Bortle 5/Bortle 6 home.
The Borg 71FL has lots of dropoff towards the edges when using the 0.72x reducer/flattener (f/4). It is much better with the 1.08x flattener (i.e., at f/6).
I have since tested the RedCat (white version) and will probably be using the latter for wide fields, while relegating the Borg 71FL to narrower fields.
Chen
