From: Sean C
Date: 2017 May 16, 20:48 -0700
"Do any NavList readers have information on vertical sextant observer errors or have made an assessment of their own observational error distribution?"
As a matter of fact, I have. Here's a breakdown of 193 observations of mine from the past few years. Many were sun sights using an artificial horizon, most of the rest were lunars. (Granted, those don't really count as "vertical".)
NB: some of these sights may have been taken with a Davis plastic sextant. Unfortunately, I did not note which sextant I used for all of the observations. The rest were taken with an Astra IIIb.
Hope you find this data useful.