First, the title: EVENING CIVIL TWILIGHT — Page 447, Lesson 419

This is a table of evening civil twilight times — a page from the almanac section of your General Navigation book. Let me walk you through exactly what you're looking at, because this is a working tool you'll use in flight planning. First, the title: EVENING CIVIL TWILIGHT. Civil twilight is the period after sunset when the sun's centre is between 0° and 6° below the horizon — that's the definition you need to hold onto. During civil twilight there's enough natural light for most outdoor activities, and for us in aviation it's the period when you can still see the horizon clearly for visual navigation. The table is organised by latitude down the left-hand side, and by date across the top. Look at the latitude column — it runs from N 72 at the top, down through 70, 68, 66, 64, 62, N 60, then 58, 56, 54, and down to S 60 at the bottom. So this table covers northern latitudes from 72°N down to 60°N, and then continues into southern latitudes down to 60°S. The N and S prefixes tell you whether the latitude is north or south of the equator. Across the top, the columns are months — April and May — and within each month there are columns for the 2nd, 5th, 8th, 11th, 14th, 17th, 20th, 23rd, 26th, and 29th of the month. So the table gives you the time of evening civil twilight for specific dates at specific latitudes. Now, the times themselves. Each entry is in hours and minutes — you'll see the format like 20 34, which means 20 hours 34 minutes. These are the times of evening civil twilight in UTC — Universal Time Coordinated, the standard time reference used in aviation. So for a given latitude and date, you read across and down to find the time. Let me give you a concrete example. Take latitude N 60 — that's the row marked N 60 in the table. On April 2nd, the time is 19 29 — that's 19:29 UTC. On April 5th it's 19 36. On April 8th it's 19 44. You can see the times getting later as April progresses — 19:52 on the 11th, 20:01 on the 14th, 20:09 on the 17th, and so on. By May 29th at N 60, the time is 21 41 — 21:41 UTC. So as the days lengthen into spring, evening civil twilight gets later and later. Now, there's something important in this table you need to notice — the double slashes — the // symbols. Look at the higher latitudes. At N 72, for most of April and May, you see // instead of a time. At N 70, the early dates show // too. Those slashes mean the event doesn't occur — at those high latitudes, during this time of year, the sun never gets as low as 6° below the horizon, so there is no evening civil twilight. The sun stays too high in the sky — this is the period of continuous daylight or near-continuous daylight you get in high latitudes in summer. So the // is a flag telling you "no civil twilight on this date at this latitude." You'll also see the letter G appearing in some cells — for example at N 72 and N 70. That G is a code used in these almanac tables. It indicates a specific condition — in this context, it marks that the sun does not reach the required depression below the horizon, so twilight conditions are continuous. When you see G, you treat it as a special case rather than reading a time. Let me also point out the S 60 row at the bottom — S 60 05 49 05 56 06 03 06 10 06 17 06 23 06 30 06 37 06 43 06 50 06 56 07 03 07 09 07 15 07 21 07 26. So at 60° south latitude, on April 2nd, evening civil twilight is at 05 49 — 05:49 UTC. Notice how different this is from N 60. At N 60 in April, twilight is around 19:30–20:00 UTC; at S 60 it's around 05:49–06:00 UTC. That's because it's autumn in the southern hemisphere while it's spring in the north — the southern latitudes are heading into shorter days, so their evening twilight times are getting earlier through April and May, not later. So the key skills here: read the latitude from the left column, read the date from the top row, find the intersection, and read the time in hours and minutes UTC. Watch for // meaning no twilight occurs, and G marking the continuous-daylight condition. And remember the definition — civil twilight is when the sun's centre is between 0° and 6° below the horizon. That's the whole table. It's a reference tool — you'll use it to know when you can still navigate visually after sunset, which matters for flight planning and for legal requirements on night operations.