NavList:

Paul Hirose, you wrote:
"The explanation lies in the 'J2000 Right Ascension, Declination' label on the coordinates."

Ah, thank you! Thank you, thank you. For this one I had a distinct feeling that I was missing something in plain sight. And I can admit, a little sheepishly, that this is one of those things that happens with passing years. See, I know (know in slow-brain mode) that annual precession is just about 50 arcseconds or roughly 0.8 minutes of arc annually, equivalent to about 1° in 72 years. So since this year is (some number greater than 2000)... that's... basically insignificant since 2000 was more or less last week, right? That's what fast-brain mode says. Oops! This is like thinking that "Cast Away" (Tom Hanks on a desert island... the movie with the analemma in it) is a "recent" movie --because 2000 was just yesterday, right? Again oops.

Of course, if one sits down and does the math (figuratively, since it's really easy math once you realize that it's nearly a quater of a century since 2000.0), it's obvious that precession shifts positions by about a third of a degree in 23 years. That means that the Moon's coordinates "of date" for mid-2023 are shifted by about 20 minutes of arc parallel to the ecliptic, which is just what I was seeing (seeing but not seeing; not seeing but should have seen). So that's that.

I agree that the other parameters in their data all appear to be fine, and I did spot checks on most to validate the data quality generally. As you say it would be more consistent to add an additional digit to the RA in hh:mm:ss format or (better) just express the RA in degrees with the same number of digits as the Declination, which is quite common in this century. That leaves only that ridiculous display bug which frequently throws off positions by 1° or 1°01'. The underlying numbers are fine.

One final thought... You mentioned that you didn't like the am/pm choice since there's ambiguity in the meaning of 12:00am. But is there? Really? This one doesn't bother me since it's more of a "jargon" ambiguity, a technicality in the sense of an over-literal interpretation of the etymological origin of "am" and "pm". The language, the words, work fine. When someone says, "12 a.m.", we all know that they mean midnight. But you're not the only one to worry about it. Here's a little chat about it from the museum staff at Royal Museums Greenwich: https://www.rmg.co.uk/stories/topics/noon-12-am-or-12-pm.

Thanks again,

Frank Reed
Clockwork Mapping / ReedNavigation.com
Conanicut Island USA