First, the title: Morning Civil Twilight — Page 457, Lesson 452

I want to walk you through the Morning Civil Twilight table. This is the kind of data you'll use in real flight planning, so let's make sure you understand exactly what it's telling you and how to read it. First, the title: Morning Civil Twilight. Civil twilight is the period when the sun is between 0° and 6° below the horizon. In the morning, it begins at sunrise and ends when the sun reaches 6° below the horizon. This table gives you the time of that end — the moment civil twilight ends in the morning, which is effectively when full daylight conditions begin for navigation purposes. Now, the structure. The table is organized by latitude down the left-hand column, from N72 at the top down through N60, N50, N40, N30, N20, N10, 0 (the equator), and S10 at the bottom. So you have latitudes from 72° North down to 10° South. Across the top, the columns are the dates — and this is important. The table runs from November 19 through January 3. Look at the column headers: 19, 22, 25, 28, then 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, then 3. So it covers mid-November through early January, which is the period around the winter solstice in the Northern Hemisphere. Each cell gives you a time in hours and minutes — that's the h and m at the top of each column. So for a given latitude and date, you read the time of morning civil twilight. Let me give you a concrete example. Take N60 — 60° North. On November 19, the table shows 07 16. That means morning civil twilight ends at 07:16. Now follow that row across: 07 23 on the 22nd, 07 29 on the 25th, 07 34 on the 28th, then 07 40 on December 1st, 07 45 on the 4th, and so on. You can see the times getting later as you move into December, then peaking and coming back down. Now here's a key observation. Look at the N72 row — 72° North. On November 19, it's 08 51. Then it climbs: 09 05, 09 20, 09 34, 09 48, 10 02, 10 15, 10 27, 10 38, 10 48, 10 54, 10 57, 10 57, then 10 53, 10 46, 10 38. Notice it peaks at 10 57 around December 22nd to 25th — that's near the winter solstice — and then starts coming back down. The times are much later at high latitude because the sun rises much later in winter up north. Compare that to the equator, the 0 row. On November 19, it's 05 20. The times stay very consistent — 05 20, 05 21, 05 22, 05 23, 05 24, 05 25, 05 26, 05 28, 05 29, 05 31, 05 32, 05 34, 05 35, 05 37, 05 38. Very little variation, because at the equator day length barely changes through the year. And look at the S10 row — 10° South. On November 19 it's 05 05, and it stays at 05 05, 05 05, 05 05, 05 05, 05 05, 05 05, 05 06, 05 06, 05 07, 05 08, 05 09, 05 10, 05 11, 05 13, 05 14, 05 16, 05 17, 05 19. Notice the times are getting later as you move into January — because in the Southern Hemisphere, this is approaching their summer, and the sun rises earlier there. So the trend is opposite to the Northern Hemisphere. One more thing to notice: the S20 row at the very bottom shows 04 48 across the board — 04 48, 04 48, 04 48, 04 47, 04 47, 04 48, 04 48, 04 49. Very stable, very early times, because it's summer in the Southern Hemisphere. So the practical takeaway: this table lets you, for any latitude from 72° North to 20° South, and any date from November 19 to January 3, read off the time of morning civil twilight in hours and minutes. You'd use this in flight planning to know when daylight conditions begin at your location — critical for determining when you can operate under visual flight rules, or when you need to plan for night operations. The key relationships to remember: higher latitude means later twilight times in winter, the equator stays nearly constant, and the Southern Hemisphere shows the opposite trend because its seasons are reversed.