"The Online Nautical Almanac" FAQ

"The Online Nautical Almanac"

Taking a computer onboard?

Some people resist to the idea of taking a computer onboard. When they go sailing, they want to stay away from those objects that make business life stressing: telephones, computers, modems... even watches.

Computers are also known to sometimes fail when we need them most. In fact, in sea conditions, most computers are far less reliable then GPS devices, defeating their use as backup navigation aids. These are indeed great arguments in favor of the old navigation methods.

That's why I decided enable the Navigator celestial calculations engine to generate old fashion "The Nautical Almanac" (TNA) pages. This support is available in two forms:

1) Navigator Light (32 bit registered version 2.5+) can produce and print nautical almanac pages. This program is available in the web for download. Read more about it

2) Online web version, open to the public. As most Internet services, it is (hopefuly) supported with advertising banners Sponsors are wellcome. Go for it.

You still need a copy of The Nautical Almanac..

Navigator engine generates the so-called "daily" pages (the ones with 3-day celestial data for planets, stars, Sun, Aries and Moon). The yellow ("increments") pages are not generated. But since they don't change from year to year, you can use an old almanac or do the interpolations with a pocket calculator.

I choose to make the Navigator daily pages as similar as possible to actual "Nautical Almanac" pages. But there are differences:

did not include the latitude dependent tables (Twilights, Sunrise, Moonrise, Sunset, Moonset).
did not include the Aries meridian passage time. I could not figure out what is the use of this number. If you know, please post me a message.
did not include the Sun's semi-diameter (SD). It's never too different from 16' anyway.
did not include the Sun's Equation of Time and meridian passage table. You may use an old almanac for the Sun's meridian passage calculations, because this table is almost unchanged from year to year. Just use the table of the same day.
did not include the Moon's meridian passage and age table.
did not include the planets' SHA and meridian passage table.
added three stars not included in most nautical almanacs :-)

I plan to include some of these numbers in future versions. Feedback from users about what features are most important is welcome.

If you compare the Navigator's almanac pages with TNA pages, you will note small differences in the numbers. These are caused by different celestial calculation methods and should not be bigger than 0.5'. This error is small when compared with other imprecisions that affect celestial navigation, and will not impact your position significantly.

Printing the almanac pages using the Navigator software

To print almanac dayly pages, do:

Go to the celestial navigation window.
Select the "Other calculations" tab.
Press the "almanac pages" button. The "Almanac Pages" window will show.
Set the initial date for the 3-day page.
Select "Aries and planets" (left side page).
Press "Build page" and "Print".
Select "Sun, Moon and Stars" (right side page).
Press "Build page" and "Print".
Click in the "Arrow" button to advance 3 days and repeat operations from step 5). Proceed until you have printed all the pages for the desired period.

In order to print your almanac pages, you have to use a non-proportional font (a font with fixed pitch). The default font is Courier New, size 7. Pages printed with this font will use a single sheet of paper (size A4). I know this is a small font, but using a larger one will result in two paper sheets for each page. You may experiment with other non-proportional fonts. True type fonts are better, because they can be resized to any small size.

Printing the almanac pages using the online web service

While web browsers show pages in the screen in the same way, printed results may differ. If you are printing many pages, I recommend you choose the minimum size of font available, in order to save paper. Another tip is to use used paper, which is frequently printed only in one side. This is much better then sending it to recicle centers and using new paper to print your almanac. Remember to protect our forests.