NavList:

Alex you wrote:

"The reason is that in general it is easier to reach high
precision with the Sun. (Because our day vision is better than our night
vision in this respect as someone explained to me on this list in
October 2004. This is confirmed by the Russian statistics too.)"

 

There is evidence that Sun-Moon lunars are easier than star-Moon lunars. But for me, Jupiter-Moon lunars produce results that are every bit as good as Sun-Moon lunars. So there really has to be some other explanation for the relative difficulty of star sights --something besides the relative lighting. 

 

As for night vision and day vision, the explanation on this list in October was not accurate. Indeed, because of diffraction, the resolution of the human eye is lower in very bright sunlight than in medium lighting. It is also lower when the eye is fully dark-adapted because of spherical aberration (and other aberrations) which become increasingly important as the iris opens. But for lunars, the eye would never be fully dark-adapted.