Now, the structure — Page 440, Lesson 403

This excerpt is a dense table of numbers — it’s the kind of page you’d find in the back of a navigation manual, not a paragraph of theory. So let me tell you exactly what you’re looking at, because it’s actually a very practical tool. What you have here is a time-of-sunrise and time-of-sunset table — a precomputed schedule that tells you, for a given latitude and date, what time the sun rises and sets. The numbers you see are times of day, written in hours and minutes, in UTC — that’s Universal Time Coordinated, the standard time reference used in aviation, sometimes called Zulu time. Now, the structure. The table is arranged so that the rows represent different latitudes, and the columns represent different dates — usually a day or a few days apart through the year. Each cell contains two times: the first is the time of sunrise, the second is the time of sunset. So when you see something like `14 41 14 45 14 51 14 57 15 04 15 11 15 19`, those are sunrise times for successive dates at one latitude. And when you see a pair like `15 02 15 06 15 11 15 16 15 22 15 29 15 36 15 43 15 50 15 58 16 05 16 13 16 21 16 29 16 37 16 45 16 52`, those are sunset times for the same dates. Let me give you a concrete example from the table. Look at the row that starts with `S60` — that’s latitude 60 degrees South. The entry `21 25 21 23 21 20 21 17 21 13 21 08 21 03 20 58 20 51 20 45 20 38 20 30 20 23 20 15 20 07 19 59 19 50` — those are sunset times, and you can see them getting earlier as the dates progress. That makes sense: at high southern latitudes, as you move toward the winter solstice, the days get shorter, so the sun sets earlier. Now, why does this matter for you as a pilot? Because sunrise and sunset times are critical for flight planning. They determine when you need to consider night flying rules, when you might need navigation lights, and when you must plan for visibility conditions. Many regulations define "night" as the period between the end of evening civil twilight and the beginning of morning civil twilight — and those twilight times are derived directly from sunrise and sunset. So this table lets you, before you even file a flight plan, look up the exact UTC times for your route’s latitude and date, and know precisely when daylight ends. Here’s how you’d actually use it. You identify your latitude — say you’re flying at 50 degrees North. You find the row for that latitude. Then you find the date you’re flying — the columns are labelled with dates, usually at intervals of a few days. You read across to the intersection, and you get your sunrise and sunset times in UTC. If you’re flying at a latitude that isn’t exactly on a row, you interpolate between the two nearest rows — that’s a standard technique you’ll use constantly in navigation. One thing to notice in the data: the times are not symmetrical. Look at the row `19 50 19 50 19 49 19 49 19 48 19 46 19 44 19 42 40 37 34 30 27 23 18 14 09 50` — those are sunset times getting later, then the next row `20 12 20 12 20 11 20 10 20 08 20 06 20 03 20 01 19 57 19 54` — those are sunrise times for the same dates. You’ll see that sunrise and sunset don’t shift by the same amount each day. That’s because the equation of time — the difference between solar time and clock time — plus the changing declination of the sun, combine to make the days lengthen or shorten unevenly. The table already accounts for all of that, so you don’t have to compute it — you just read it. Also notice the latitude labels — you’ll see rows like `S60` for 60 South, and other rows with just numbers like `30`, `45`, `50`, `56`, `58`. Those are latitudes in degrees. The table covers both hemispheres, so you’ll see both North and South latitudes, and the times will behave differently — in the southern hemisphere, the sunset times get earlier as you approach their winter, while in the northern hemisphere they get later as you approach summer. Now, a practical caution. This table gives you standard times for a specific longitude — usually the central meridian of a time zone or the Greenwich meridian. If you’re operating at a different longitude, you have to correct for your longitude — roughly 4 minutes per degree of longitude, because the sun moves across 15 degrees of longitude per hour. So the table gives you a baseline, but you adjust it for your actual position. Let me also point out the format of the times — they’re written as four digits, like `14 41` meaning 14 hours 41 minutes, or `21 25` meaning 21 hours 25 minutes. In aviation, you’ll always use the 24-hour clock, so there’s no AM or PM — 14 41 is 2:41 PM, and 21 25 is 9:25 PM. So, to summarise what you’ve got in front of you: a precomputed sunrise/sunset table organised by latitude and date, giving times in UTC, used for flight planning to determine daylight hours, night operations, and twilight calculations. You read it by finding your latitude row and date column, interpolating if needed, and correcting for longitude. That’s the whole tool. It’s not glamorous, but it’s the kind of reference you’ll pull out before every flight that might cross twilight. Now, do you want me to walk you through a specific example — say, how you’d interpolate between two latitudes, or how you’d apply the longitude correction?