i had a 16" Meade Lightbridge for some time
if i remember correctly i did view IC 1101 an elliptical galaxy at 1.15 billion light years distance and 13.2 mag.... it was fairly easy in moderately dark skies sqm 20.8 or so
if your talking point source object i remember viewing 3C273 a quasar at 2.4 bilion light yeas distant ... again an easy grab at a mag of 12.9
matt
A 16" should fairly easily pick up galaxies in the Abell Galaxy cluster 2065 in Corona Borealis.
There are at least 3 or more at mag.15-15.5 in that cluster, at 1.05 billion light years.
I've seen 3 in my 12.5" in skies of mag.21.4+.
Quasars might be visible out to 8 billion light years, so I wouldn't count those.
I attach a few distant galaxies for your consideration.
Const / Galaxy / Group association / Mag. /Distance