You didn't list an f ratio for the refractor. 770mm sounds like a 110mm f7 (eg William Optics Fluoro Star 110).
That gives FOV 98.8x65.9 arcmin without the flattener and 116.3x77.5 arcmin with the 0.85[/QUOTE]
Oops! My bad, it is a William Optics FLT 110 f7.0 the reducer is actually .8 too.
Thx for the tip
