This was the chapter I didn’t quite get to on the online course, so now I’m counting on having brought the right books, Google or Youtube tutorials are not available out here. I found it a little frustrating that I’d paid for an online theory course, but hadn’t considered that there was no option to download the course, so, with the exception of a few pages I’d printed, I had no access to any of it whilst at sea, but I guess most people do the theory course first.
And now I’m about to get fully acquainted with new favourite book number two, this book only contains numbers, lots and lots of them. I like this book, I can see when I have the answer right or wrong even though I can’t always see why at this point, but I can see that the numbers either “fit” or they don’t.
This book enables us to refine our estimated position using the Sun, Moon and planets at any time of day or night. Part of my morning routine, as per the instruction books, has been to take a morning sight on the Sun. I’m at roughly 20 degrees north, it is November and I quickly observe how fast we are spinning as the Sun rises above the horizon at a fair old rate and every observation requires some twiddling of knobs on the sextant to keep the sun on the horizon. At this time of day we take a series of five sights, record each one to the second and then head for shade.
I’m also going through the same process with the afternoon to try and use sight reduction to ascertain a position line. I seem to be able to collect the information I need from the sextant and use the sight reduction tables, but the logic of how the plotting sheets work is elluding me, the more I look, the more lines I draw and rub out and draw again the less it makes sense. But I’ll keep trying, it will click eventually. Until that happens the whole thing is driving me a little mad and without Google, Youtube or another human being to explain it to me it could be a very long learning process.
The next step is quite lengthy when you’re as mathematically inept as I am. We need to work out the average of the five sights, “add them all together and divide by five” I hear you say, neither my brain or my calculator can cope with adding up three columns of degrees, minutes and seconds, all of which are 60s. I am a metric girl, I was brought up with tens in columns, not sixties.
So for each morning (and afternoon) Sun sight I draw a graph. As a result I think I am the inventor of “Navigators Graph Paper” where the squares are divided into sixes instead of tens. We do this to come up with a number and average of our five sights, this is the angle we have measured between our horizon and the Sun, applied some corrections and written down as “Ho”. This is where the real excitement begins, this is where I find out if I have correctly estimated our longitude, latitude and local hour angle and correctly observed the Sun. If all of these things are correct the number I have (Ho) should be very close to the number I will obtain from Favourite Book number 2. “Ho Mo To” has been the mantra my shipmate has been whispering for the last few days. It turns out that once upon a time he had taken celestial navigation classes and this phrase was drilled into them. “Ho Mo To” will mean nothing to you, but it meant the world to me once the penny dropped. Seeing the numbers align themselves on the page is an immensely satisfying process, especially for the mathematically challenged, and a welcome confirmation that all of the above are good.
Rather disappointingly after all this the best we get is a line on a chart, all we know is that at the time the sight was taken we are somewhere on this line. “But where?” That infernal question again… “somewhere on that line” is very vague, especially when the line is very very long. I still feel rather lost in all of this!
I know the next thing I must do is work out what time I think noon will be, take our noon sight and with any luck, finally get my head round the mystery of the Plotting Sheet…