Let me explain how to read it, because the layout is the key — Page 444, Lesson 409

I want to walk you through the sunrise table. This is a standard piece of navigation data you'll use to find the local time of sunrise for any latitude and date. Let me explain how to read it, because the layout is the key. The table is built around two variables. Down the left-hand side, you have latitude, labelled "Lat" in degrees. You'll see rows for North latitudes — N 72, N 70, N 68, N 66, N 64, N 62, N 60, N 50, N 40, N 30, N 20, N 10 — then the Equator at 0, and then South latitudes — S 10, S 20, S 30, S 35, S 40, S 45. So the table covers from 72 degrees North down to 45 degrees South. Across the top, you have the months and days. The columns run from February, with days 16, 19, 22, 25, 28, then March with days 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, then April with day 2. So the table spans mid-February through early April. Now, the body of the table gives sunrise times in hours and minutes — the "h" and "m" at the top of each column stand for hours and minutes. The times are local time of sunrise for that latitude and date. Let me show you how to read one entry. Take the row for N 60. On February 16, the sunrise time is 07 hours 37 minutes. On February 19, it's 07 hours 28 minutes. You can see the times getting earlier as you move through the columns — that's the days getting longer as spring approaches. Now watch what happens as you move down the latitude rows. At N 72 on February 16, sunrise is at 08 hours 51 minutes. At N 60 on the same date, it's 07 hours 37 minutes. At N 50, it's 07 hours 10 minutes. At N 20, it's 06 hours 29 minutes. At the Equator, it's 06 hours 11 minutes. And at S 30, it's 05 hours 41 minutes. So the pattern is clear: the higher your latitude in the Northern Hemisphere in late winter, the later the sunrise. As you move south toward the Equator and into the Southern Hemisphere, sunrise gets earlier. That's because in February and March, the Southern Hemisphere is tilted toward the Sun — it's their late summer — so they get earlier sunrises, while the far North is still in the grip of winter with late sunrises. There's one more thing to notice. Look at the Equator row, 0 degrees. The sunrise times there barely change — 06 hours 11 minutes, 06 hours 10 minutes, 06 hours 09 minutes, staying right around 06 hours. That's because at the Equator, day length is nearly constant all year round. The Sun rises at essentially the same time every day, regardless of season. Now, one important detail about how the table is organised. Notice that within each latitude row, the times are not all in a single continuous line. The row is split into two lines of figures. For example, at N 60, the first line runs from 07 hours 37 minutes down to 05 hours 24 minutes, and then the second line continues from 05 hours 58 minutes onward. This is just a formatting convention — the table wraps the data so it fits on the page. When you read a row, you follow the first line across, then drop to the second line and continue reading left to right. The second line continues the same sequence of dates. Let me also point out the southern rows, because they behave differently. At S 10, the times start at 06 hours 02 minutes in February and then — here's the interesting part — they get later as you move into March and April. At S 30, February 16 is 05 hours 41 minutes, and by early April it's around 06 hours 11 minutes. So in the Southern Hemisphere, the trend is reversed: sunrise is getting later as autumn approaches there. The days are shortening. So the complete picture is this: this table gives you local sunrise time for any latitude from 72 North to 45 South, for dates from February 16 to April 2. You enter with your latitude and your date, and you read off the hours and minutes of sunrise. The times shift with latitude because of the Earth's tilt, and they shift with date because the seasons are progressing. That's the whole table. When you're ready, we can move on to how you'd actually use this in a navigation problem — interpolating between latitudes and dates to get a precise sunrise time for your exact position.