NavList:

Wolfgang Köberer wrote:
"Siebren van der Werf, a retired nuclear physicist, has written a couple of articles about atmospheric refraction"

I have briefly skimmed but haven't read any of his papers on refraction. Also of interest for navigation is his paper on the issue of wave height and dip. His co-author on that paper is Igor Shokaryev who was a regular contributor of NavList posts for several years. The article deals with an interesting issue... We know that the sea horizon from which we must estimate height of eye to get a value for dip is composed of overlapping wave crests in the distance. If waves are all more or less similar in size, then the appropriate height of eye is simply height above the top of the typical wave crest. But what should you do with a more random distribution of wave heights? They investigate that analytically and by simulation in the article. It's food for thought...

"He has also published an article about the use of lunars by Joshua Slocum.

This is much less useful. Although the various versions of his article are apparently / ostensibly about that famous instance of a lunar shot by Joshua Slocum about a half-century after they were commonly used at sea, the article is, in fact, completely un-historical. It is fundamentally a speculation about 'what might have been' with almost no basis in reality except for the rather mundane astronomical circumstances. The article, first of all, lays out those circumstances of the lunar scenario: what would the lunar angle have been? what were typical altitudes for the Sun and Moon? Thirty years ago (this was around 1994) when van der Werf was puzzling on this, determining astronomical circumstances for analysis of historical celestial navigation was not simple. But it is now trivial, and it has been easy for roughly twenty years. That renders the scenario analysis in his article obsolete. The article continues with an opaque mathematical analysis of the process of clearing a lunar using a relatively difficult method that Joshua Slocum very likely would not even have recognized. This is where the whole thing becomes un-historical. There is zero evidence today on Slocum's work that day --there is no extant logbook-- and therefore all of the math in the article is nothing more than unfounded speculation. We know that Slocum was a relatively ordinary celestial navigator, self-taught in his early career, with a fascination for older methods (...probably because Slocum himself was "old" at this date, as he saw it himself, and he turned to his own rather antique skills). The over-mathed analysis in van der Werf's paper supports the illusory and misguided notion that Joshua Slocum must have been some sort of math genius because only a math genius could comprehend such equations. That was wrong in general and wrong in this specific case.

"He may not be well known on the other side of the Atlantic."

His work is not too hard to find online, and I'll repeat the link that you provided in your message: https://siebrenvanderwerf.nl/. I mentioned recently that some non-english-language sources are not well indexed in common English-biased search engines (including Google). Since Siebren van der Werf has written mostly in English and his website is in English, that's not a problem, and his papers are well-indexed.

Frank Reed