Yes, the Naval Observatory table is what I used also. Kept it pinned up to my bulletin board at work to estimate how dark it would be when I got off the train and unlocked my bike. Night-time lights are different from day-time, especially since I had a "dark zone" of 2 km where there were no streetlights and no traffic. Lovely under a full moon with snow on the ground and lights off. (Don't tell my wife...)

As per John E, the analemma explains it, and check out the really cool composite photos where one of the exposures (the first, presumably) captures a solar eclipse! The two lobes of the figure 8 are not symmetric, owing to the eccentricity of the earth's orbit.
Fundamentally, the sun is a good calendar (once you figure out Leap Year) but not a very good clock because it runs fast or slow, depending on time of year. The effect is an artefact of imposing an invariant clock time on a wandering timepiece.
The key to understanding is recognizing that any body moving in an elliptical orbit speeds up and slows down during its orbital journey (conservation of angular momentum). When it is close to the centre of mass located at one focus of the ellipse (which can be taken to be the centre of the sun even though it's not quite), it moves faster. This is what the earth is doing right now, 4 January being perihelion. As it swings around and gets farther away, it slows down until 4 July, then it starts accelerating again. These dates are pure coincidence (other than being six months apart by necessity) and have no relation to the seasons. Once you recall that the earth's orbital velocity it not constant but varies predictably through the year, you can see how solar noon will not occur at the same clock time every day and not all days are 24 hours long. Rather, the error will accumulate progressively, then start correcting so that the solar day is, on average over the course of the year, its familiar 24 hours. Since sunrise and sunset are keyed to the noon mid-point of the sun's apparent journey across the sky, these times will vary as well when measured by an invariant clock. If you have a sundial, you have to add or substract minutes each day to make it agree with a mechanical clock. If you didn't correct it for "elliptical variation", you would see earliest sunset and latest sunrise and the lowest noon sun all on 21 December, equidistant from solar noon. Someone a few minutes of longitude away, also with an uncorrected sundial, would see the same thing, but the two of you would see them at slightly different times. And both of you would be late or early for your appointments which are regulated by clock time. By coincidence, the maximal variation from clock time occurs in the dark months of November and December when we are most attuned to them.

I think this is important because:
Everyone 'knows" that Copernicus and Gallileo proved the earth revolves around the sun. But they didn't, really. The honour belong to Johannes Kepler and Sir Isaac Newton.
The recognition that the planets (and the satellites of planets) move in ellipses (although some, like Venus. are very close to perfect circles) was a fundamental achievement in working out planetary mechanics. It drove the final nail into the coffin of the dogma of a stationary Earth at the centre of the universe. Copernicus had the heretically counterintuitive idea that the planets revolved around the sun in circular orbits, true. It didn't predict the observed apparent movements of the heavens any better than the astrologers could do using the Ptolemaic view of complex circles within circles of an unseen celestial machine cranked by who-knows-what?. Great simplification made this conceptual leap attractive but really it was just a shift in mathematical frame of reference. Nothing about the earth-centered view was disproven by Copernicus's formulation. Even Gallileo's observation that the four moons of Jupiter* he could see with his telescope were clearly revolving around Jupiter and not around the earth could be explained away as a special case of the Devil trying to tempt us, with his evil instruments and fake news, to test our faith. Indeed, the very careful later telescopic observations by Tycho Brahe, an earth-centrist, showed discrepancies in the position of planets predicted by the heliocentric circle model, a "Gotcha!" which called the very idea into question and seemed to vindicate the Church. Johannes Kepler's incalculable gift to science was to recognize that in those discrepancies lay the foundation of a new theory: when he fitted the planets to elliptical orbits, the discrepancies were resolved (at the limits available in the day.). Then it was for Newton to develop the theory of gravitation (aided by calculus) to propose a mechanism for what made it all work....which scientists are still working on to this day.

I just think it's gratifying that you can use simple observations (aided by timepieces not available until recently in human development, say, mid-18th Century) to take a step toward understanding the true nature of the heavens. (To make an analemma you have to observe the sun at exactly the same clock time every day, a meaningless concept before the naval chronometer.) I'm not embarrassed to say I am profoundly moved by this.
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* If you've never done so, I urge you to go out with a pair of ordinary binoculars some clear night that Jupiter is visible and look for the Galilean satellites. You can see them from a city street, you don't need a super dark sky, although no moon makes it easier. Steady the binoculars against a telephone pole or the roof of a car. One or two moons are easy to see and you can verify that you don't always see all of them -- sometimes they are behind the planet, or sitting on top of it where Jupiter's light obscures the satellite as seen with 7X binoculars. (Galileo was able to describe the passage of the moons across the face of Jupiter with his 30X? telescope before they went around the back.) This simple exercise with very basic equipment should fill you with a sense of wonder that you can make an observation about the nature of the universe that was absolutely inaccessible to all humans who had ever lived up to that moment.