Notification

If you downloaded «AstronavXls_ver_14.1» in the past few weeks, you may have found weird results in the plotting of the sextant position data given as an example. The cause is that someone modified the input data on the worksheet opened as a «preview» on the blog site when you click on the file name in the download area. If you make any modifications in that «preview», it is made directly in the shared file in my One Drive account associated with the blog. So, please, don't change anything on that «preview», just download the file using the menu in the «preview»: File/Save as/Download/Download a copy. Once on your computer, you can change whatever you like.

Also, nowaday with all the security installed on all computers, when you try to open the Excel file on your own computer, you may have a warning saying that the macro-instructions on the Excel worksheet have been blocked. To make the file active, you should right-click on its name, then select: Property/General/Security: Unblock (if you trust me...).

Normally, after downloading the file on your own computer and authorizing the macro-instructions in the Excel worksheet, you should erase the «example» data by pressing «reset all data» on each sight sheet, and enter your own data. Have fun.

Thanks for your trust.

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.

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.

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.

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

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

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.

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.

AstronavXls, version 13.2

Correction of minor bugs and extension of the calculation capability for the intersection of Circles of Position at a large distance from the azimuth line.

New «AstronavXls user's manual», version 13.1

Minor changes to Section 3.02 on the celestial sphere projection graphs, to clarify the description (hopefully).

Improved artificial horizon

Here are pictures of the improved version of my homemade artificial horizon.
It uses a 5x5 in (125x125 mm) front face mirror (Edmund Optics), 200 turns per inch (tpi) adjustment screws (Kozak Micro Adjusters), and a precision surveyor's level (tube obtained at Level Developments Ltd, with an accuracy of 2 sec of arc). The level mount also includes a calibration 200 tpi screw. I tested it with three-stars fixes during the summer and obtained results better than 1 mile as compared to my GPS position. No more twilight time limitation!...

 

New «Sextant sight series plotting sheet v3.0»

This update of the «Sextant sight serie plotting sheet» allows the plotting of three sight series in the same Excel Workbook instead of a single series with the previous document. This is in conformity with the AstronavXls processing of a maximum of three astronomical sights for a position Fix. Observed altitude sextant data series with time of observation can be entered for three different celestial bodies. The progression and precision of the sight series are graphically visualized and sights with excess offset may be eliminated. More accurate results can be obtained by mean of a polynomial bestfit curve.
The data entered as examples on the individual sheets were obtained from test measurements last summer, using an artificial horizon (which explains the observed altitudes high values, double of normal values).

AstronavXls, version 13.1

Correction of a bug with the «Reset All Data» button, which erased a few cells in the «LOP Plot» worksheet. This problem did not affect the calculation results.

"Sextant sight series plotting sheet v2.1"

A bug associated with the "Erase all data" button caused a stop of the program. This bug was corrected, and I took the opportunity to include the possibility to note the name of the celestial body and the date of the sights.

Artificial horizon for the DIY land navigator

Just in case you break your GPS, here is a suggestion to take sextant sights anywhere, anytime (with a cloudless sky): nothing beats an artificial horizon, made of a solid homemade tripod, an old bathroom mirror with added level adjustment screws, and an equally homemade surveyor's level from a tube obtained through Level Development Ltd, with a precision of 2 arc seconds. Very good reflexion coefficient, but a mirror quality not quite so good. A  first surface mirror would be more adequate to avoid the double reflexion (easily discriminated from brightness difference). Well, another purchase to come...

"Sextant sight series plotting sheet v2"

Modification to the sight series plotting sheet, to allow the removal of data points considered as having an abnormal offset, for an improved bestfit curve. The removal from the curve is obtained by changing to red the Font color for the hour data. The falty point is not erased and can be reestablished by changing the Font color back to black.

AstronavXls, version 13.0

In this new version, all three Sight data worksheets have been provided with a check box for meridian passage (midday) sights. Checking the midday sight checkbox on the Sight sheet transfers the corrected GHA value of the celestial body as the Assumed Position (DR) Longitude entry, after conversion to equivalent East or West longitude. The effect is to align the azimuth line of the celestial body to the observer’s meridian at the time of transit. The latitude is found at the intersection of the circle of position with the azimuth line. The observer’s coordinates at transit time are displayed in the Meridian Passage section on the LOP plot worksheet.

Prior to the advent of the GPS, surveyors determined benchmarks coordinates with great accuracy by averaging the meridian transit of several stars, using a theodolite. The new version of AstronavXls allows to test that technique with up to three meridian passage sights, by averaging the obtained coordinates, upon the click of a check box. The technique is not very useful on a moving boat, when one is limited by the time constraint of twilight and a real horizon. However it can very well be applied with an artificial horizon, at a fixed position, where time and available stars are no limits, for the sake of comparison with the more standard method of obtaining a fix. Personally, I made my own artificial horizon with an old 6-inches bathroom mirror, properly leveled using a precision surveyor level, accurate to 2 seconds of arc.

AstronavXls, version 12.8

Correction of a bug associated with the click box for meridian passage sights.
Two new converter tools were added in the Sight data sheets: a converter from the longitude difference between two meridians to the equivalent time difference in the sun passage, and the reciprocal, a converter from the difference in the sun time passage between two meridians to the equivalent difference in longitude.
Paul

AstronavXls, version 12.7

Fix of a minor problem occuring in the display of the GHAy projection label, in the time diagram of each "Sight" sheet (the South pole view), whenever the sight type (star, sun, planet or moon) was changed.
Paul

AstronavXls version 12.6

Since AstronavXls plots true circles of position (COP) rather than lines of position (LOP), all reference to LOPs have been modified to COP, except for the name of the plot sheet "LOP Plot" which has been preserved because its is used as a reference marker in the macro commands. I had kept the LOP identification because people are more familiar with the term, but it creates confusion. The equations used to perform the astronomical calculations or the various corrections have been added on the "Sight" sheets, either in a display box, or as comments attached to the appropriate description cells. Some minor bugs or errors have been corrected.
Paul