The maximum field is determined by the barrel field stop, and, therefore, by the focuser tube diameter. Or 2-in barrel and a 2-in focuser, this should be somewhere around the 48mm thread diameter for the filters, 47 to 48 mm maximum field
You can use the first two calculators at Wilmslow Observatory's site, just Google Wilmslow observatory calculator to fool around with various combinations, but, I did this years ago and again recently.
Maximum, or near maximum fields in a 2-in focuser can be had with an APM UFF 30mm, a good choice with a fast refractor and, I would imagine, a good choice with a fast reflector but I don't know for sure, or a 31 Nagler. The APM will be a little shorter the maximum, and the Nagler should hit the maximum field. There are, I believe, 70 degree eyepieces in the 34 to 36 mm range that should provide similar large fields, but I would run them through the Wilmslow calculator to get exact numbers for comparison
Many folks like the longer focal lengths and narrower fields of 40 mm eye pieces, but I like maximum fields and maximum field of view, just my preference.
On the moon you will almost certainly suffer problems with the secondary shadow. On less intensely bright objects, the secondary shadow may or may not be bothersome as Bradfran mentions.
Edited by markb, 02 December 2020 - 01:40 PM.