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Emergency Nav for Calculators
This document is designed to summarize techniques that can be used for ocean and coastal navigatin without conventional tools or resources, but with a navigation calculator at hand. It is intended to be used with the StarPilot navigation calculator, but the principles can be executed with any preprogrammed celestial navigation calculator. It is landscape format on legal paper.
How to Average Sextant Sights
When doing sight reduction by hand from a moving vessel, it is crucial for optimum accuracy to properly evaluate a series of sights of the same body to obtain the best sight. This article explains how to do it. It is part of the "standard techniques" that are being slowly lost with time. Omitted from the latest editions of Bowditch, you must go back at least to the "green" editions to read about it. [30 kb pdf]
How to Use Plastic Sextants
Tells all about plastic sextants and how to use them, illustrated with real data from offshore and on-land sights. Compares metal and plastic sextant data. Includes crucial procedures for getting the most out of these versatile alternatives to more expensive metal models.
How we do Lunars
The StarPilot program in both calculator versions and in the PC versions has a routine for computing lunar distance. Just enter your lat and best guess of your longitude along with the lunar distance you measured and the hack time you measured it and the program computes your longitude and watch error. This article explains the procedures we use to do that computation.
Lunar distance computations
We cover how we solve lunars in the StarPilot in a different article. Here is another approach from Dr. Wendel Brunner. He provides an in depth article here on how to do this with a calculator, including some history of the method and even applies his method to some of our earlier data.
Lunar Distance using the Stark Tables
A useful review of the Stark Tables. Written by Jan Kalivoda.
Lunar Example
This is the example we used to illustrate the StarPilot lunar solution, and we have also used this one for practice with the Stark Tables. Date is May 7, 2000. It is typical sun-moon lunar with good results.
Lunars HQ
An online site that covers all aspects of lunar distance measurements, plus history, instructions, predictions, and even an online computer to analyze your sight data if you do one. Excellent resource. (We need to compare these online computations with our starpilot results, which we tested rather extensively over the years.)
Solar Index Corrections
How to make an accurate measurement of your sextant index correction using the sun's diameter. Includes forms for the process. This was the standard method of land-based explorers in the 1800's. It is especially valuable for doing lunar distance measurements since they must be as accurate as possible.
About chart datums
A plain language article on the meaning and history of chart datums. Very interesting reading.
Three Body Sextant Piloting
A brief explanation of Three Body Sextant Piloting and Three-arm protractor use.
Tidal Current Tricks from Starpath
In waters with strong tidal currents, we often need to plan passages at slack water. This article explains simple tricks for estimating how long the current speed will be below a specific speed.
Tidal Theory
A series of 6 articles on the astronomical issues that drive the tides. Presented as web pages.
Boxing the Compass
We finally made an in-depth discussion of boxing the compass along with the rules for doing so and a table for every quarter point. Plus we raise the question, just why did they do it this way?
e-vector solutions
Any electronic charting program can be used to very easily solve any vector problem that arises in marine navigation. These include current vectors, wind vectors, and relative motion vectors in radar applications. In each of these applications there are several types of vector triangles that often need to be solved. The method applies to any of them. This is a very slick procedure, and we are only sad that we did not think of this several years ago when e-charting programs started to be popular.
If you have not looked in a while, the world of EPIRBS has changed a lot. The older class A B C S etc will not be supported, and we must move on to the new 406 MHz EPIRBs are the only way to go these days. They cost a lot more, but they are much more dependable. This article reviews the situation and gives the end dates of earlier systems.
Precise great circle computations
This is a note about using great circle computations in general and more specifically as they might apply to cel nav sight reductions using GPS units. A rather detailed point, but important to us, because somewhere we have stated this incorrectly. This is to correct that publication, where ever it is.
US Army Corps of Engineers
A massive list of engineering manuals on line in pdf format on various subjects.
Radar and The Nav Rules
This document takes each reference in the Nav Rules to radar, directly or indirectly, and then explains it in detail, word for word. There is also included an in depth discussion of Rule 19d on what should be done when another vessel is detected by radar alone... or by hearing it without visual contact.
Radar a many-splendored thing
Marine radar has several, more or less independent, applications to safe, efficient navigation. One is collision avoidance, for which it is the undisputed king of the electronics dashboard, another is actual position fixing, for which it competes with GPS (favorably in many cases) and in any event is always a very convenient way to verify a GPS position, and finally radar offers a unique and powerful aid to what might be called general vessel piloting. Specific procedures within each of these applications are described in this article.
Weather by email
This note provides instructions on how to use email to request weather maps and text data from the NWS. The products are then sent back to you as email attachments.
What kind of pressure do you want?
Explains true pressure versus sea level pressure when your barometer is at home or office at some elevation... and how to calibrate a barometer to either setting.
Why to care about accurate pressure
In the old days, and even in most books today, barometric pressure has been treated as a relative quantity. No one tried to obtain or proclaimed a need for actual pressure, just relative. It is going up or down, and how fast, is all that was preached.... and indeed very few authors have been very specific at all about how fast is fast? That is different now. And accurate pressure is indeed important to efficient, or at least tactical, navigation. Here we explain why. [30 kb pdf]