Lunar Tables

The lunar distance and proportional logarithm of up to six navigational bodies are computed every three hours, just like they were in the 1906 Nautical Almanac.  The supporting proportional logarithm, Bowditch log trig tables, moon augmented semidiameter, and second difference tables provide everything else you need.


Where values are required from the current Nautical Almanac to clear the lunar distance (to determine refraction, parallax, and dip corrections), those pages are also displayed to demonstrate all steps to do a lunar.

ezLunars generates the pre-computed lunar distances as they were generated in the Nautical Almanac through 1906.  All other tables needed to clear the lunar distance and determine universal time are also included.

Moon’s Augmented Semidiameter


This table provides a moon semidiameter from its approximate altitude and the HP value from the Nautical Almanac Daily Data page.


This is needed to separate the moon semidiameter from the value returned from the altitude correction table in the Nautical Almanac.

Supporting Nautical Almanac Correction Tables


The refraction, parallax dip and semidiameter values for the lunar sights still require these corrections from the Nautical Almanac.


The tables cannot be accessed directly, but are displayed and highlighted when showing the values to use for the lunar sights.

Drag to Highlight then

Pinch to Zoom

  

All ezLunar tables can be highlighted just by touching the screen and dragging your finger to the row and column you are looking for.


All tables also support pinch to zoom, so no more squinting to read your table!

Save or Print

  

Just tap any ezLunar table to get a menu to output the page.  Send it directly to a wireless printer or save it as a PDF file to print later. 


The PDF files can be exported directly to Dropbox or saved to the ezAlmanac document directory where they can be accessed from iTunes.


More info on exporting to Dropbox or iTunes can be found here.

Proportional Logarithms Every Second Over Three Hours


This table is used along with the proportional logarithm value in the pre-computed lunar distance table to determine the universal time from the cleared lunar distance.

Proportional Logarithm Second Differences


This table provides an additional time correction to account for an abnormally high change in the proportional logarithm in the pre-computed lunar distance table.  This can occur when the object used for the lunar is too close to the moon.

Object Selection for Pre-Computed Tables:


  1. 1.The selection of objects for pre-computed data is made from the Sun, navigational planets and the following stars: Altair, Fomalhaut, Hamel, Aldebaran, Pollux, Regulus, Antares, Spica, and Markab.

  2. 2.The selection is limited to the objects within 120º from the moon (max sextant arc).

  3. 3.Objects on the opposite side of the Sun as the Moon are discarded since they will never be visible at the same time as the Moon.

  4. 4.If more than 6 objects are available after the above checks, the 6 with the lowest proportional log values are used.  These with be the objects closer to the path of the Moon.

Bowditch Log Trig Tables


The Bowditch Log Trig tables are provided to clear the lunar distance using the Borda method as it was done before computers and calculators.


These compact tables provide the logarithm of 6 trigonometric function for angles 0º-180º in only 45 pages.

Supporting Nautical Almanac Daily Pages

  

The semidiameter of the Sun and HP of the Moon from the Nautical Almanac daily pages are required when doing lunars.


The tables from ezAlmanac are provided as needed to demonstrate where to get the values needed when your are doing Lunars manually.