By Denis Glennon
The desire to use a sextant swells strongly in the veins of all cruisers who choose to leave the shoreline and venture beyond the horizon. There is an art in handling a sextant. Taking a sight, reading the tables, doing the maths, finally placing a diminutive cross on a chart and declaring confidently, “That’s where we are!” appears almost magical to the uninitiated while in the middle of the ocean.
GPS has obviated the practical requirement for retaining a sextant onboard and using celestial navigation. Anxious cruisers carry two GPSs, and skeptics of the reliability of electronics, carry three. This is OK. Many cruisers get pleasure from having electronic charting systems and onboard computers driving their autopilots. Others have cockpits that look like something out of “Star Wars” and words like “database’ and “interface” proliferate their vocabulary. Each to his own!
Yet, even when surrounded by the most modern navigational aids, the heart of every cruiser harbors a yearning for a place in the fraternity of celestial navigators. Blue-water sailors derive immense fulfillment from taking a good sun, moon, or star sight, but when faced with a position line located in the middle of Alice Springs on a cloudy day, many wish (some pray) for an alternative to the ubiquitous tables in the Nautical Almanac.
There are navigators who would pay handsomely for a panacea to the propensity for errors when using the tables, especially after four days of shooting and not much sleep, and doing the maths at a nav station that just won’t remain still. For ‘senior’ navigators the error rate appears to grow inversely to the ability to read columns of tables that persistently diminish in size, despite the assiduous upgrading of spectacles.
Within the booklet’s 50 pages lie every table you will ever require. Better still, for those with onboard laptops, there is an accompanying software program, which, upon entering the normal sextant readings and individual parameters, will calculate the intercept and azimuth instantaneously, and magically error free.
Easynav provides a set of instructions, rather than tedious explanations, which will safely and accurately take every cruiser from a sextant sight to a position line. There is no need to understand terms that have scared thousands of willing cruisers away from celestial navigation (e.g. Declination, DR, Greenwich Hour Angle, Geographical Position, Local Hour Angle, Sidereal Hour Angle, and the like). You only need a short lesson from a fellow cruiser who knows how to use a sextant correctly, and by following the easy steps in Easynav, you can determine where you are, with confidence and good accuracy.
But this article is not about the pros and cons of GPS. It is about the gratification that comes from experiencing the delightful amalgamation of the traditional craftsmanship of taking a sextant sight and common sense. Having used Easynav for a number of years I cannot help but think that Frank Dinkelaar gave it to cruisers because he got tired of seeing us do it the hard way!
A yearly published nautical almanac will always be more accurate than a long term table. But, in my experience it is the quality of the sight itself that is the determining factor of the accuracy achieved. On a sailboat this comes down to the motion of the deck and the experience of the sextant user.
During a recent 600-nautical mile offshore passage I had the opportunity to compare results from the Easynav approach with those obtained by an experienced cruiser while undertaking his AYF Yachtmaster’s Ocean Certification, using the Sight Reduction Tables for Air Navigation HO 249. With Easynav the time taken to calculate intercepts/azimuths was much shorter, the accuracy of position lines as dependable, the frequency of double-checking calculations far less, and nerves and temperament were less frazzled! This pragmatic tool is a significant contribution to the world of blue-water cruising, but why stop there?
Until then I will still hold on to my Easynav manual and my trusty Tamaya, and pray I will not find too many of my position lines telling me I am one nautical mile north east of Kalgoorlie!
Editor's Note: Easynav may be obtained from F.Dinkelaar, P.O. Box 2019, Christchurch 8005, New Zealand.
Denis Glennon holds AYF Yachtmaster Ocean Certification. Despite navigation instructors shaking their heads in dismay, he believes if a navigator happens to be exactly where he thinks he is, it is purely accidental, since celestial navigation is not an exact science; rather it's a craft in which judiciousness and wisdom play critical roles, both of which cannot be taught.
If you'd like to contribute to Our Readers Write section, please send your submissions to [email protected].
|Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)|
|Thread||Thread Starter||Forum||Replies||Last Post|
|SEACOURSE Auto Helmsman||ROSA||Gear & Maintenance||16||09-19-2016 01:17 AM|
|The helmsman||CharlieCobra||General Discussion (sailing related)||13||09-10-2011 12:01 AM|
|Wow! Pinta's Helmsman is Great!||Winderlust||Seamanship & Navigation||10||06-17-2009 12:32 PM|