The columns are the days of the month — Page 449, Lesson 428

I want to walk you through this sunrise table, because it's one of the most practical tools you'll use in general navigation. This is a table that gives you the time of sunrise at various latitudes throughout the summer months — June, July, and August — and it's laid out so you can read the local mean time of sunrise for a given latitude on a given date. Let me first explain the structure, because once you see the layout, the numbers will make sense. The table is divided by latitude, running from N 72 degrees down through N 60, N 50, N 40, N 30, N 20, N 10, then 0 (the equator), and down to S 10 — that's 10 degrees south. So it covers the northern hemisphere summer, where the sun rises early, and it extends just a little into the southern hemisphere. The columns are the days of the month. Look at the top: you have June, then July, then August, and under each month the days are listed — 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, then 3, 6, 9, 12, 15, and so on. So the table isn't giving you every single day; it's giving you sunrise times at roughly three-day intervals. The times themselves are in hours and minutes — that's the "h" and "m" you see at the top, standing for hours and minutes. Now, here's the key thing about this table: the times are in local mean time. That's an important distinction — this is not standard time, not zone time, not UTC. It's the local mean time at the observer's meridian. So when you read a value, you're getting the moment the upper limb of the sun appears above the horizon, expressed in local mean time for that latitude. Let me walk you through a few rows so you can see the pattern. Start at the top, at N 72 degrees. In early June, the entry is marked with a "G" — that stands for continuous daylight. At 72 degrees north in early summer, the sun never sets, so there's no sunrise to record. As you move through June and into July, you start seeing actual times: 00 49, then 01 30, then 01 58, then 02 21. So at N 72, the sun first dips below the horizon enough to produce a sunrise later in the season, and the times are very early — just after midnight, around 00 49, creeping toward 02 21 by late July. Drop down to N 60. Here you have times like 02 39 on June 1st, then 02 42, 02 45, 02 49, 02 54, 02 59, 03 04, 03 10, 03 17, 03 23, 03 30, 03 37, 03 44, 03 51, 03 58, 04 06, and 04 13 by mid-August. Notice the trend: as summer progresses, sunrise gets later. The sun rises later each day after the summer solstice, and the table captures that beautifully. Now look at the equator, the row marked 0. On June 1st, sunrise is at 05 59. Then 06 00, 06 01, 06 01, 06 02, 06 02, 06 02, 06 02, 06 03, 06 03, 06 03, 06 03, 06 03, then back to 06 02, 06 02, 06 02, and 06 01 by mid-August. At the equator, sunrise is essentially constant — around 06 00 — because the length of day doesn't change much there. The variation is only a minute or two across the whole summer. Now, here's a really important detail I want you to notice. Look at the row for N 10, the one just above the equator. The times are 05 42, 05 43, 05 43, 05 44, 05 45, 05 46, 05 46, 05 47, 05 48, 05 48, 05 49, 05 49, 05 50, 05 50, 05 50, 05 51, 05 51. So at N 10, sunrise is around 05 42 to 05 51 — earlier than at the equator, because in the northern summer, the northern hemisphere gets earlier sunrises. And at S 10, the row below the equator, the table starts with 06 — and you can see the times are later, around 06 00 or just after, because it's winter in the southern hemisphere. So the pattern across the whole table is this: the higher the northern latitude, the earlier the sunrise in summer, and the more it shifts as the season progresses. At N 72 you're looking at times around 00 49 to 02 21 — very early morning. At N 50, you're around 03 53 to 04 49. At N 30, around 04 48 to 05 10. And at the equator, a steady 06 00 or so. One more thing to note: the "G" entries. Those appear at the high latitudes — N 72, N 70, N 68, N 66 — in the early part of the season. That's the period of continuous daylight, when the sun doesn't set at all, so there's no sunrise time to tabulate. As the season moves on, the sun starts setting again, and actual times appear. So when you use this table in practice — say you're planning a flight and you need to know when it'll get light at a particular latitude on a particular date — you find your latitude row, find the date column, and read the local mean time of sunrise. That's the whole tool. It's a quick reference, but it's built on the fundamental idea that sunrise time depends on both latitude and date, and it gives you the exact local mean time for that combination.