First, the layout — Page 447, Lesson 421

I want to walk you through the sunrise table in your General Navigation manual. This is the kind of table you'll use operationally to work out daylight hours for a route, so let's make sure you can read it properly. First, the layout. The table is titled "SUNRISE" and it's organised by latitude, which runs down the left-hand side in degrees — N 72, N 70, N 68, all the way down through N 60, N 50, N 20, N 10, the Equator at 0, then S 10, S 20, S 30. So the rows are latitudes, north and south of the Equator. Across the top, the columns are dates. The table covers May, June, and July. The date columns run from May 17, 20, 23, 26, 29, then June 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, then July 1. So it's a three-month window, sampled every few days. Now, the numbers in the body of the table — each entry is a time, given in hours and minutes. For example, at N 68 latitude on May 17, the sunrise is 01 38 — that's 01:38. On May 20 it's 01 20, May 23 it's 00 58, May 26 it's 00 25. So the times are in hours and minutes, and they're local times of sunrise at that latitude on that date. You'll also see the letter "G" scattered through the table, particularly at the high northern latitudes — N 72 and N 70, and parts of N 68. That "G" stands for a period of continuous daylight — the sun never sets at all. So at those latitudes in late May and June, there's no sunrise time to record because the sun doesn't rise and set; it just stays above the horizon. That's the midnight sun phenomenon. Now let's trace what the table is telling you about how sunrise times change. Look at N 60. On May 17, sunrise is 03 19. Then it gets earlier: May 20 is 03 12, May 23 is 03 06, May 26 is 03 00, May 29 is 02 55, June 1 is 02 50. It keeps getting earlier until around June 16, where you see 02 36 — that's the earliest sunrise of the year at that latitude. Then it starts getting later again: June 19 is 02 36, June 22 is 02 37, June 25 is 02 39, June 28 is 02 39, July 1 is 02 42. So the table shows the full swing — earliest around the summer solstice, then creeping later. Let me show you the same pattern at the Equator, latitude 0. On May 17, sunrise is 05 53. It stays very stable — 05 53, 05 53, 05 53, 05 53, then 05 54, 05 54, 05 55, 05 55, 05 56, 05 56, 05 57, 05 57, 05 58, 05 59, 05 59, 06 00. So at the Equator, sunrise barely changes — it's almost constant, just a few minutes of drift across the whole three months. That's because at the Equator, day length is nearly constant all year. Now compare that to the higher latitudes. At N 50, May 17 is 04 12, and it gets earlier to around 03 50 by mid-June, then later again. At N 40, May 17 is 04 55, dipping to about 04 45 in June. At N 30, May 17 is 05 06, dropping to about 04 58. At N 20, May 17 is 05 23, and it only dips to about 05 20. So the pattern is clear: the higher the latitude, the bigger the swing in sunrise time across the season, and the earlier the sunrise gets in summer. Now let's look at the southern hemisphere. At S 10, May 17 is 06 07, and it gets later through the period — 06 07, 06 07, 06 08, 06 09, 06 10, 06 10, 06 11, 06 12, 06 13, 06 13, 06 14, 06 15, 06 16, 06 16, 06 17. So in the southern hemisphere during May, June, and July — which is their winter — sunrise is getting later, not earlier. That's the mirror image of the northern hemisphere. At S 20, May 17 is 06 20, and it drifts later through the 20s and 30s. At S 30, May 17 is 06 39, then 06 40, 06 42, 06 44, 06 46, 06 47, and it keeps climbing. So the key operational takeaway: this table gives you sunrise time as a function of latitude and date. You read your latitude down the left, your date across the top, and the intersection gives you the local sunrise time in hours and minutes. The "G" entries mean continuous daylight — no sunrise at all. And the pattern to remember is that sunrise times swing most dramatically at high latitudes and barely at all at the Equator, and that the southern hemisphere is the mirror of the north because its seasons are opposite. That's the whole table. You'll use this alongside the sunset table to compute total daylight for a leg, so make sure you're comfortable reading both latitude and date off it quickly.