Look at the structure first — Page 453, Lesson 444

I want to walk you through something very practical now — a real navigation table from the book. This is the kind of page you'll actually use in flight planning, and it's all about sunrise times. Look at the structure first. The page is a grid. Down the left-hand side you have latitude values, marked N50, N20, N10, then 0, then S10, S20, S30, and so on down to S60. So the rows are latitudes, from 50 degrees North all the way down to 60 degrees South. Across the top, you have a row of numbers that run from 17 38 down through 16 19 and beyond. Those are the sunrise times, expressed in hours and minutes, in UTC. So 17 38 means 17 hours 38 minutes UTC. Now here's the key idea. The table tells you, for any given latitude and any given date, what time the sun rises. But notice — the times get smaller as you move across the top row. That's because the table is arranged so that as you move from left to right, you're moving through the year — from one date to the next. The numbers decrease because sunrise is getting earlier as the season progresses. Let me show you how to read it. Pick a latitude, say N50. Follow that row across. You'll see times like 17 38, 17 31, 17 25, 17 18, 17 12, 17 06, 17 00, 16 54, 16 49, 16 43, 16 38, 16 33, 16 28, 16 23, 16 19. Each of those is a sunrise time at N50 for a successive date. Now here's the clever part — the table is built so that the same time appears in multiple rows. Look at the value 17 38. It appears at N50, and it also appears further down. That's because the table is designed so that you can interpolate — you can find the sunrise time for a latitude that falls between the listed rows. Let me give you a concrete example. Suppose you're at N50 and you want the sunrise time. You read across the N50 row and find the time that matches your date. But what if you're at N45? You'd look between the N50 row and the N20 row, and you'd interpolate — estimate the time that falls proportionally between the two. Now, the bottom of the table has a special label: SUNRISE. That tells you this entire table is for sunrise times. And you'll notice the times at the bottom, around S60, are much later — 18 21, 18 28, 18 36, and so on up to 20 26. That's because at high southern latitudes in this season, the sun rises much later in the day. Here's the practical point. This table is a quick reference. Instead of calculating sunrise from first principles — which involves spherical trigonometry and the sun's declination — you just look up your latitude and your date, and you read off the time. That's the whole purpose of the table: speed and accuracy in flight planning. Now, one thing to notice. The times are in UTC, not local time. So when you use this table, you have to convert to local time for your actual operations. And the times are for the moment the upper limb of the sun appears above the horizon — that's the standard definition of sunrise. Let me also point out the interpolation more carefully. Look at the value 17 38 again. It appears at N50, and it also appears at N20 — wait, let me check. At N20, the first value is 17 48, not 17 38. So the same time doesn't necessarily repeat across rows. The interpolation is between the rows for a given date column. Here's how it works in practice. You find your date column. You read the sunrise time at the latitude above your position and the latitude below your position. Then you interpolate — you estimate the time that falls proportionally between the two, based on how far your latitude is between the two rows. Let me give you a real example. Suppose you're at N35, and your date column shows 17 31 at N50 and 17 43 at N20. Wait — let me check the actual values. At N50, the second value is 17 31. At N20, the second value is 17 45. So at N35, halfway between N50 and N20, the sunrise time would be roughly halfway between 17 31 and 17 45 — that's about 17 38. That's the interpolation. You're estimating the time for a latitude that falls between the listed rows. Now, the table also shows you something important about the geometry of sunrise. Look at the top row, N50. The times decrease steadily — 17 38, 17 31, 17 25, 17 18, 17 12, 17 06, 17 00, 16 54, 16 49, 16 43, 16 38, 16 33, 16 28, 16 23, 16 19. That's a steady decrease of about 6 to 7 minutes per column. That tells you sunrise is getting earlier at a fairly constant rate at this latitude and season. Now look at the bottom, S60. The times increase — 18 21, 18 28, 18 36, 18 43, 18 51, 18 58, 19 06, 19 14, 19 22, 19 30, 19 38, 19 46, 19 54, 20 02, 20 10, 20 18, 20 26. That's an increase of about 7 to 8 minutes per column. So at S60, sunrise is getting later at a slightly faster rate. That asymmetry — the different rates at different latitudes — is a direct consequence of the Earth's axial tilt and the sun's changing declination. The table captures all of that in a simple grid. Now, there's one more thing I want to point out. The table has a column structure where the times are arranged so that the same time appears in adjacent columns. Look at the bottom rows — you'll see values like 18 02, 18 03, 18 05, 18 07, 18 09, 18 11, 18 13, 18 15, 18 17, 18 20, 18 22, 18 24, 18 27, 18 29, 18 32, 18 34, 18 37. The increments are irregular — sometimes 1 minute, sometimes 2, sometimes 3. That irregularity reflects the changing rate of sunrise as the season progresses. Here's the key takeaway. This table is your quick reference for sunrise times at any latitude and date. You read the latitude row, you find your date column, you read the time, and you interpolate if your latitude falls between rows. The times are in UTC, and they represent the moment the sun's upper limb appears above the horizon. That's the whole table. It's a tool — a fast, accurate way to get sunrise times without doing the spherical trigonometry yourself. And that's exactly what you need in flight planning, when you're working out whether you'll have daylight for your departure or arrival.