I was just using Alan Adler's "Sec" program from Sky & Telescopes
free download area to analyze secondary sizes, central obstructions,
and image brightness, but I couldn't figure if given all other
things being equal (16" reflector, f/4.7, 3.1 inch secondary) would
the Nagler 2" 17mm Type 4 produce a brighter or dimmer object at the
field edges compared to the new Nagler 1.25" 16mm Type 5 EP. (I guess
it boils down to the L value between the EPS, which I do not know).
Does any one know if one is brighter than the other???

Thanks for any help,
Phil