ezLunars

Lunars are easy when you have a Nautical Almanac and the pre-computed lunar distance tables!  The lunar distance tables have not been published in the Nautical Almanac since 1906 but ezLunars has brought them back.


The lunar distances of up to 6 navigational bodies are provided at 3-hour intervals, along with the proportional logarithm value needed to interpolate the distance to the universal time at the time of your observation.  A proportional logarithm table, the Bowditch log trig tables, moon augmented semidiameter, and second differences table are also provided.  All tables can be easily printed to a wireless printer or saved to a PDF file for use outside the app.


Like ezAlmanac, ezLunars includes an “Expert” function to guide you through the process of making the observations and using the tables to compute universal time.

Learn to do lunars as they were done when the pre-computed lunar distance tables were published in the Nautical Almanac!  ezLunars brings back the lunar distance tables and the process to clear the distance and find UT.

Check Out the Help Pages

The “More Information” button on the top right of the first Expert tab screen will take you to the first help page (this page).  From there you can select any of the links at the top of the page to go directly to the information you are interested in.


Each individual expert function also has a “i” button.  Press this button to go directly to the help page for that particular function.


The help pages are HTML but are included in the app download, so they are always available.

Try the Expert Functions

The Expert functions allow you to quickly do lunars using the Nautical Almanac and the additional lunar tables.  All intermediate values used for the function are shown, with the values from the Nautical Almanac or lunar tables displayed as a button.  Touch any of these buttons and you will be immediately taken to the page or table the value is found with the row and column highlighted.

Practice Using ezLunars

Read through the help page “Your First Lunar!” and you will see how you can practice with ezLunars even before you head outdoors or on the sea with your sextant.


The ezLunars expert includes a “Make Observation” function which predicts the expected Hs of your lunar observations considering the current DR position and all corrections.  Just set your DR position and select the object you want to shoot.  When you enter your observations using the predicted altitudes from the Make Observation function, the lunar will resolve to the current universal time!

Highlight then Pinch to Zoom

The example above shows highlighting a value from an Expert screen, but highlighting is also supported on all other lunar tables by just dragging your finger on the table.


After entering a table using one of the application tabs, drag your finger to highlight the row and column just above your finger tip.  When you have selected the desired row and column, you can now pinch to zoom-in to view the highlighted value with ease.  Pinch to zoom-out to full screen again and touch away from the current highlight to clear the highlighting.

Learn About Lunars

Everything you need to know about lunars is available right from the app. Press the “More” button and Select “About Lunars” to  let George Huxtable explain it to you.  There are many different methods to clear the lunar distance but the 2 described here (Young and Borda) are the ones used by ezLunars.


You will also find  “Longitude Mathematics”, a paper by Wong Lee Nah.  The initial chapters are a great history of lunars and the foundations for the mathematics.  Chapter 8 does a systematic explanation of the mathematics arriving at Young formula (in the middle) and finally to the Borda log trig formula.