A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2014 Jun 5, 16:20 -0700
Greg, you wrote:
"Not sure about his discussions on refraction. Perhaps something got lost in translation."
Well, maybe. It certainly isn't true that refraction is greater in the afternoon, though I've heard this before as a "navigator's rule of thumb" (in other words, a legend). It can be true, though, that refraction is subject to greater variability at different times of day since there can be layering in the temperature distribution of the air close to the water's surface, especially in calm conditions. Note that this isn't really variability in refraction per se. That is, you wouldn't have cause to use different refraction tables for the Sun and stars. It's actually unusual refraction at the horizon, or as we know it in NavList discussions, "anomalous dip". His comment that there is no refraction at all for stars surely must have been due to something lost in translation, as you suggest. But at night, anomalous dip should be less of a concern, and maybe that's what he meant --that unusual refraction at the horizon is less of a concern for star sights.
You also wrote:
"I did find his technique of making observations without a scope and both eyes open interesting. Being able to take a round of stars on a moonless night is something that would have to be confirm."
I think this one will depend more on the individual. Certainly binocular vision (both eyes open) has more benefits than we usually believe, and it may well be that, at least for some people, the horizon is easier to perceive on a dark night with both eyes open. On the other hand, a scope with some magnification increases contrast significantly. I wouldn't be surprised if some observers can do better picking out the horizon with a 7x scope than with both eyes open and no magnification.