Let me orient you to the structure — Page 447, Lesson 422

I want to walk you through what this page actually is, because at first glance it looks like a wall of numbers. This is a sunset table — a tabulated set of data that gives you the local mean time of sunset for a range of latitudes and dates. In professional navigation, you don't guess when the sun goes down; you look it up, and this is the kind of table you'd use. Let me orient you to the structure. Down the left-hand side, in the column labelled Lat., you have latitudes running from N 72 degrees down to N 52 degrees — so this particular page covers northern latitudes from 72°N down to 52°N, in steps of two degrees. Across the top, the columns are labelled by month — May, June, July — and then subdivided into individual dates: the 17th, 20th, 23rd, 26th, 29th, then 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, and back to 1. So you're reading across for the date and down for your latitude. Now, the numbers themselves. Each entry is in the format hours and minutes — the header row shows h and m for hours and minutes. So, for example, at N 68° on May 22nd, the table gives 22 20, meaning sunset occurs at 22 hours 20 minutes local mean time. At N 66° on May 17th, it's 21 40 — 21 hours 40 minutes. Here's something important you'll notice: at the higher latitudes — N 72° and N 70° — the entries are marked with the letter G. That G stands for a special condition: at those latitudes, around this time of year, the sun does not set — it's the period of continuous daylight, what we call the midnight sun. So instead of a time, the table gives you G to indicate that sunset doesn't occur on those dates at those latitudes. Now watch what happens as you move down the latitudes. At N 68°, you get actual times for the later dates — 22 39 on May 20th, 23 03 on May 23rd — but the early dates are still G. As you go further south, to N 66° and below, you get real times all the way through. So the table is showing you the geographical progression: the further north you are, the later the sunset, and the more dates fall into that continuous-daylight regime. Let me read a few specific values so you can see the pattern. At N 64° on May 17th, sunset is at 21 13. At N 62° on May 17th, it's 20 52. At N 60° on May 17th, it's 20 35. Notice how, for the same date, the time gets earlier as you go south — that's the latitude effect on sunset time. There's also a subtle detail in the data: the times increase through late May and into June, reach a maximum around the summer solstice, and then decrease again into July. Look at N 60°: on May 17th it's 20 35, it climbs to 21 28 around late June, then drops back to 21 25 by July 1st. That's the seasonal swing — the sun sets latest near the solstice and earlier as you move away from it. One more thing to note: at the very bottom of the page, you'll see the word SUNSET as a label, and the data continues down to N 52°, where on May 17th sunset is at 19 59. So the full sweep of this page is: from 72°N, where the sun never sets in this period, down to 52°N, where you have normal daily sunsets with times around 20 hours. In practice, you'd use this table by taking your latitude and the date, and reading the local mean time of sunset directly. That time is what you'd then convert and apply in your navigation planning — for example, when you need to know when daylight ends for a flight plan or for calculating twilight operations. The key professional points to remember: the G means no sunset — continuous daylight — and the times are in local mean time, hours and minutes, not UTC.