NavList:

I used PM (singular) in terms of the PM half of a AM-PM pair.  Averaging multiple AM-PM pairs to get LAN is likely to provide more accurate LON. There would be a different correction for each PM sight since there would be a different elspased time and distance traveled for each pair unless you were stationary.

I wondered where Hewitt got the correction table, he didn't cite a source that I could find.  Do you know what the formula is?

I found a PDF of Vol-3 of the 1938 Admiralty book and am reviewing the chapter on effects of MOO (Motion Of Observer) on a noon sight and will be studying that for a bit.  Thanks for the hint about where to look.

Currently I am teaching the general solution in my celestial navigation class using the nautical almanac, HO-249 and Davis-15s.

During the 4th or 5th class I am going to discuss other solutions, tricks and alternatives to everything:

For almanacs: Kolbe & long term solar (& stellar) almanacs.

For sight reduction: 214, 229 (&Schlereth), 211 (Pepperday & Balyliss), 208, Davis (NAO-SR)

Sextant choice: box/pocket, Davis-3, Bris, SNO-T vs the risks of other Ebay sextants. I'm pretty sure somebody is making replica Tamayas and trying to pass them off as the real thing which makes me wonder about many other sextants being offered.  The SNO-T is kinda unique and I think harder to counterfit so I'm more trusting about what is advertised.

Noon sights: Schlereth, Burch, 

Gatty (which is kind of a noon sight).

Lunars: traditional, Chichester and Letcher

Reverse reduction from a known position to find accurate time.

Starfinders

When I get to Noon sights I intend to discuss Burch as he seems to have the best discussion of how to use them for both LAT & LON but he doesn't discuss MOO.  also his book is easy to find.

I am partial to Burch's book also because it fits in a 50cal ammo box with a Davis-3, small shortwave, solar battery charger, backup GPS, NiMH batteries, watches and the necessary plotting gear.

Schlereth's book does not really fit and the almanac is seriously outdated though easily fixed and it's hard to find.   Kolbe would fit or Kolbe & Ageton since I seriously don't like Davies/NAO-SR.

Re: Motion Correction for Longitude: sights around Noon
From: Frank Reed
Date: 2025 Mar 1, 05:12 -0800

Robert VanderPol II, you asked:
"Would adjusting the PM sight up or down by distance traveled (nm) N or S be an acceptable alternative methodology?"

Yes, absolutely. The tabular correction works well, and it's quicker. But simple addition of altitude offsets works well, too. One detail here: you said "the PM sight" as if you're considering only one. That's not terrible, but this process is significantly more effective if you have a half-dozen or a dozen sights centered on local apparent noon. That improves the accuracy considerably.

You mentioned Hewitt Schlereth's book devoted to this topic, and I do recommend it, but it's getting hard to find. The same process is discussed in the Admiralty Manual of Navigation from a theoretical point of view, and we can certainly re-derive it. Anyone interested in working through that? There's a relatively simple equation involving tan(Dec) and tan(Lat) that will tell us how many seconds we need to add or subtract to adjust for the large impact of observer motion on a longitude derived from a near-noon Sun curve.

Frank Reed