AstronavXls navigation freeware

Introduction to this site

This celestial navigation software allows the reduction of sextant sights. The software is based on macro-enabled Microsoft Excel Worksheets. With primary input data from the Nautical Almanac, it gives a graphical representation of the various parameters used in the solution of the spherical navigation triangle, while minimizing the need of correction tables. Up to three sights can be processed and the results are plotted, showing azimuth lines and circles of position. The intersections of the circles of position are computed, as well as the resulting mean position.

One must keep in mind that electronic navigation aids (GPS and others), although indispensable nowadays because of their efficiency and accuracy, will always be subject to technology contingencies, their status of maintenance and, not the least, the variability of the world mutual trust. Celestial navigation remains above all those constraints… And when nothing else works, the good old sextant will always come in handy… as long as one knows how to use it!

I developed this software in an attempt to put together the knowledge acquired from navigation courses from the Canadian Power Squadron, and I offer it for free to all who have an interest in sextant celestial navigation as a challenge, to preserve the knowledge and know-how, or out of sheer curiosity.

Following that line of thought, this software can be considered more as a teaching aid and may contain errors affecting navigation. Hence, there is no warranty pertaining to the accuracy and the results obtained while using the product.

How to download AstronavXls and other documents

- In the “Download Documents” section, to the right, click on the document you want to download (for example, The latest version of AstronavXls);

- A sample of the file will open on the screen. This document is not functional as the macros are not enabled.

- To download the original Excel file, click on the “File Tab” on top left of the screen, and select: Save as/Download a copy /Microsoft Excel (.xlsm); a text box will appear and offer you a choice to open the file in Excel mode, or save it to your computer.

- The first time you open the downloaded Excel document, it may open in “protected mode”. Click on “Activate modification”, and save the document.

- For pdf files, simply click "Download" in the toolbar.

About the Excel file

The Excel file containing the Astronav software is a Microsoft Office 2013 version (tested with Office 2021) with a *.xlsm extension. The “m” in the extension indicates that the file includes “macro functions”. Therefore, the “macro-enable” option must be activated in your Excel setup. The procedure to do so is as follows, once the file is opened:

- Click on the File tab (upper left corner), then «Excel Options/Trust Center/Trust Center Settings/Macro Settings/Enable all macros».

- The procedure may be slightly different in earlier versions of Microsoft Excel.

The file that you are downloading contains, by default and as an example, old sight data taken many years ago, as I was taking the CPS courses. The worksheets may be re-initialized to 0 by clicking on the button «Reset all input data to 0». Nautical Almanac data can be obtained from the following site: http://www.tecepe.com.br/scripts/AlmanacPagesISAPI.isa.
All you have to do is to enter a date and the data for 3 consecutive days will be displayed.

The advantage of the Excel file is that it may be renamed and saved with all your sight data sets, in as many copies as you want. Hence it is good practice to keep a copy as a clean template.

Fair winds and navigation!

Paul Chevrette

Wednesday, June 28, 2023

New AstronavXls 14.1

Minor corrections for a better Web presentation prior to downloading.

The verion number of the User’s Manual has also been updated to correspond to AstronavXls 14.1.

Monday, February 27, 2023

Update of the user's manual (version) 14.0_b

Two Appendices have been added to the user's manual, for the sake of completeness.

Appendix A describes the mathematical calculations to plot the circles of position (COP) , using spherical trigonometry.

Appendix B explains the scheme used to determine the intersection of two COPs, using lines of position moving tangentially along the COPs and converging to their intersection point. The Excel VBA code to accomplish this task is also described with detailed comments.

Monday, October 10, 2022

AstronavXls version 14.0

In this new version, AstronavXls 14.0 has been revised to modify the few remaining erroneous LOP (Line of Position) reference identifications to COP (Circle of Position), mainly in the plotting sheet, now named "COP plot". The plots are real COP derived from the sextant measured celestial body altitude.

The user's manual has also been revised accordingly and a few more corrections were made.

Saturday, February 26, 2022

About the Download Procedure

Some changes were made regarding the downloading procedure. Previously, the original documents were kept on the "Google drive" server and upon clicking their hyperlink in the "Download documents" section, the document was forced to open in the "Google document" application, not fully compatible with "Microsoft Excel". The appearance of the "Excel document" was not representative of the original, particularly regarding the graphic content, and this false appearance was not very incitative to download the original.

The original documents are now stored on "One drive", owned by Microsoft, and open in a compatible "Excel viewer", showing the true features of the Excel worksheet (although not fully operationnal because the macro functions are not enabled). Once the document is opened, clicking the "File" tab followed by "Save as/Download a copy" in the rolldown menu allows proper downloading of the plain "Excel *.xlsm" original.

Text (pdf) documents have a "Download" tab in the tool bar.

Paul

Wednesday, February 23, 2022

New: Universal Plotting Sheet v1.1

The Universal Plotting Sheet instructions have been modified to indicate that before changing any scale setting, one should make sure that the zoom factor of the sheet (bottom right, when the toolbar is active) is set at 100%. After, you may change the zoom and the scales will follow.

Paul

Friday, March 26, 2021

Universal Plotting Sheet v1.0

When offshore, you need a plotting sheet adjusted for the mean Latitude of the area you are navigating. Some printed sheets do exist which are preset to a specific Latitude, such as the #974 plotting sheet, with meridian spacing set to Lat 45°, or other fixed values. If your navigation extends over several latitudes, you have to bring a whole set of sheets with different mean latitudes. With this Excel Universal Plotting Sheet, you can enter any Latitude value and the meridian spacing with associated scales will automatically adjust to the desired value. This Excel Worksheet requires enabling the «macros» in the Excel File/Options/Trust Center Settings.

However, if you are taking a navigation course and a specific preset sheet is recommended for an exercise, make sure that you select the same mean Latitude with the Universal Plotting Sheet, otherwise your results may differ significantly from the expected ones.

Monday, May 4, 2020

New AstronavXls version 13.3

A few more corrections: removed the distance limitation in the computing of COP intersections. Set the axis divisions adjustment on automatic, to avoid cluttering of the scales when displaying larger areas.