Interactive Spreadsheets for Celestial Navigation
Polaris




In the northern hemisphere, the observed altitude of Polaris indicates your latitude.  This value is only approximate because Polaris does not sit exactly above the North Pole.  If you know your longitude, you may use the polaris.xls spreadsheet to improve your latitude determination by accounting for the small distance of Polaris from the Pole.  Enter Universal Time (UT) of your observation in row 2, longitude in cell A5, and observed altitude (Ho) of Polaris in cell B5.  Your latitude is displayed in cells D5 and E5.  Cell F5 contains the azimuth of Polaris.  In row 10 you may see the Geographical Position of Polaris, which is computed from the UT.  The SHA may differ a little from published almanacs but this does not affect the spreadsheet’s latitude result.

The algorithms encoded in our almanac spreadsheets (including Polaris) have a large range of validity both into the future (see our blog posts about the years 2013 and 2014), and the past.

The following image shows the spreadsheet polaris.xls.




Summary for spreadsheet polaris.xls:

Input cells: A2, B2, C2, D2, E2, F2, A5, B5
Output cells: D5, E5, F5
Intermediate cells: B10, C10, D10, E10, F10


The example preset in this spreadsheet is taken from p. 275 of the Nautical Almanac, 2009 Commercial Edition.




If your longitude is unknown, you may instead use the polaris_lha.xls spreadsheet with the LHA of Polaris as input in cell A5.  This LHA can be estimated by inspecting the relative orientation of nearby star patterns (most likely the Ursa Minor constellation) with respect to the horizon.  All other data are placed in the same cells as in the polaris.xls spreadsheet.


The following image shows the spreadsheet polaris_lha.xls.



Summary for spreadsheet polaris_lha.xls:

Input cells: A2, B2, C2, D2, E2, F2, A5, B5
Output cells: D5, E5, F5
Intermediate cells: B10, C10, D10, E10, F10


The example preset in this spreadsheet is taken from p. 275 of the Nautical Almanac, 2009 Commercial Edition.

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