Celestial-Navigation

Mum was to be Franda II's navigator. Being a school teacher, she was more capable and interested in learning navigation than Dad. Dad had other responsibilities as captain.

A retired English couple lived up the road from the Clendon Cove farm. Colin was a retired ship's captain and had fallen in love with New Zealand on one of his visits. He and his family immigrated to NZ, and Townie and Mrs T finally retired to Jacks Bay. They were surrogate grandparents to Kathryn and I. On the occasional times we girls stayed overnight, Townie would tell us bedtime stories. I loved the way that he made them up on the fly.

Once Townie knew of the family's plan to sail around the world, he took it upon himself to teach Mum celestial navigation. This involves taking sights with a sextant and some exact maths.

First of all, Mum practised with the sextant at home. Because she lived in a valley with no horizon, she would put a pan of water out on the lawn; this would be her horizon. She practised with the sextant, bringing an image of the sun down to kiss the water's surface in the pan.

She held the sextant in her right hand and ensured the dark filters were over the mirror so she didn't hurt her eyes. Facing the sun and looking through the eyepiece towards the horizon, her left fingers squeezed the clamp to release the index bar. Slowly, she pushes this away, altering the angle of one of the mirrors. When she sees the sun's image near the horizon, she releases the clamp and, using the fine-tuning knob, makes minute changes to settle the sun's image on the horizon. Twisting the sextant slowly, she would see the sun pendulum kissing the horizon. The reading would give the sun's altitude(angle) above the horizon.

This she practised for many weeks. It is easy to be accurate when the earth and pan of water are still. The real challenge would come from Franda II's moving deck. A whole new learning curve.

Mum was already an experienced sailor. But similar to Rock climbing's rule of thumb of three contact points with the rock at all times, the rule of boats is the same. So, with both hands holding the sextant and feet planted firmly on the deck, she still needed the other point of contact. This would preferably be a hip, buttocks or thigh, pushed firmly against the doghouse, mast, stay or any other strong point.

Being only firmly attached from the waist down allowed Mum's upper body to stay reasonably still. Her lower half would move with the yacht while the upper would maintain level with the horizon. It takes a lot of practice to maintain balance and more time to perfect keeping the sun shining in the sextant's mirrors while everything else moves around you.

Mum would have another person take the exact time she had the sun kissing the horizon. With this reading of the sun's angle above the horizon and the exact time, she could follow through the steps and come up with a longitude. Franda II was somewhere on this East-West line.

The Log would have Franda II's headings, time and speeds since the previous position. From this, Mum would work out distance and heading and extend Franda II's last position by ruler onto this new East-West line she had drawn on the chart. As this was the first sight of the day, the last known position could be and often was 20 hours old. This would give a DR(Dead Reckoning) position. Hopefully, it would close, but it's not accurate. There could be current and/or "Drift" from the wind pushing the yacht downwind that would not be considered.

Another site about 1100 would again give a longitude line. Moving the morning's longitude line in the direction and distance Franda II had sailed until they crossed would provide another DR position.

The Midday sight is a little different and returns the Latitude. Franda II would be somewhere on this North-South line. Mum needed to find the angle and time when the sun reached its Zenith (its highest point above the horizon). She would position herself firmly and check regularly if the sun was still climbing. She would roughly know today's Zenith time from the previous day's Zenith time. As the angle got close to the previous day's Zenith, the timekeeper would keep an eye on the handheld chronometer waiting for Mum's "Now". When it came, they would jot the exact time down and ask Mum for her sextant reading, jotting this beside the time.

Next, Mum would set herself up at the chart table and work magic. This Latitude line would cross the morning's sites line, and a position would be marked and brought up to date with the last couple of hours of Franda II's travel. This would give a pretty accurate position.

After some calm days out on the Bay of Islands, where Mum successfully pinpointed Franda II's position multiple times, a two-day trip was planned out of sight of land. This was to give her some experience with ocean swells and no land in sight to practice her newfound skill.

Townie was also on board, and their positions were marked on the map within 1 nautical mile, so both teacher and student were confident. Townie also taught Barbara coastal navigation, which is very different but much easier to "see" one's error but in many ways more dangerous as there was land to run aground on.

Mum also learnt to take star sites and work them out. On our circumnavigation, she only used star sites if we had been without sun for a few days and were closing in on land.

Often, when many hundreds of miles from land, only a morning and midday sight would be taken. There was no need to know precisely where Franda II was. She was not going anywhere in a great hurry.

Franda II's crew worked on the premise that she would travel 100 NM in 24 hours. So, if the next port was 1000NM away, they assumed it'd take 10 days.