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A celestial tune-up in time for landfall

Jan 1, 2003

At 0815 I wiped the sleep out of my eyes and worked my way from the chart table to the companionway. My wife Kay looked first at me and then her wristwatch -- she still had 45 minutes remaining of her watch.

"How come you're up early?" she asked.

"The satnav is dead," I said, bracing myself as Kavenga, our Lord Nelson 41, took a long roll to port.

"Sure it's not just a fuse again?"

"No, the fuse is okay, and there's 12 volts at the plug. It's really dead this time."

Kay looked at me in silence for moment. "What was it you said when the knotmeter died?"

Four days earlier the digital knotmeter had ceased to function shortly after our departure from Whangarei, New Zealand on the 14th of May. Kay had asked me then if not having the knotmeter for the passage to Fiji posed a serious problem. I had said no, the satnav gave us speed-made-good nearly once an hour. That would be sufficient for maintaining a respectable DR on the open ocean.

The irony of my faulty logic finally dawned on me. As long as we had the satnav, the need for an accurate DR track had seemed less critical. Now that we had no satnav and really needed an up-to-date DR, we had no speed instrument.

"You know all those wood chips under the helm seat?" I said, avoiding her question.

"Yeah?"

"They're about to get used."

I had Kay take two chips to the bow while I moved to the stern pulpit. The Monitor steering vane continued handling the steering chores, driving Kavenga dead downwind, as she ran wing-and-wing on a northerly course. On my command, Kay threw the first chip into the water, even with the bow and just outside the bow wake. I punched the stopwatch button on my digital watch as the chip hit the water and again as it passed me at the stern -- a fraction over five seconds. The second chip yielded the same result within hundredths of a second.

Using five seconds and Kavenga's length-on-deck of 41 feet, I ran the calculation for speed on my wristwatch calculator -- 4.9 knots, about what I would have guessed. We were back in the DR business. With a good supply of wood chips, a few sun sights and evening stars, we would have our navigation once again under control.

Having to rely solely on celestial was not a new experience for me. During the Vietnam War, I had served as navigator aboard the ammunition ship, U.S.S. Vesuvius. For navigational electronics, the ship had radar and a microwave-sized loran that was only useful near Hawaii and the West Coast. Several passages across the South China Sea and the Pacific had necessitated thousands of celestial observations.

Now it was like a reunion of old friends when I removed the Tamaya Jupiter sextant from its case. Like my ambivalence about the dead knotmeter, this feeling of confidence was soon to cause problems.

At 1057 ship time, I took my first sun sight of the passage. One advantage I had over my Navy days was the presence of a laptop computer running the J. Henry navigation package. Since the computer would do most of the tedious work, I took six sights versus my usual two while Kay recorded the times and altitudes in my sight log. The one big disadvantage compared to my Navy experience was the lack of a high, relatively stable platform from which to shoot. Being able to let the computer analyze and average the best of the six sights was a welcome compensation for having to shoot from a rolling, pitching, yawing deck only four feet above the waterline.

The LOP from the averaged sun sights, crossed with an LAN latitude line, yielded a noon position that roughly agreed with the noon DR position. I say "roughly" because the noon DR wasn't exactly fresh. I had gotten into a nasty habit of not plotting every satnav fix. In fact, after discovering the satnav in its Tango Uniform condition, I noted on the passage chart that I hadn't plotted a fix since 1430 the previous day. Ouch!

Well, you see, the "logic" goes like this: the satnav saves the last 12 fixes in memory, so why get all excited about plotting every single one of them as they occur? The trouble with this rationale is that it's difficult to retrieve those fixes from memory when the instrument is as dead as yesterday's roadkill. I had picked this time, on this passage, to become derelict in my duty.

The lack of a respectable DR position and close agreement between it and the sun-LAN fix annoyed me, but celestial conditions were good, and I was sure a round of star sights at evening twilight would allow me to begin a proper DR track. In fact, my confidence level was still high enough for me to tell Kay that I wanted to try to make landfall on Minerva Reefs. I had heard some of the other boats on our evening ham radio net talking about the anchorages inside the two circular reefs the night before. They weren't far off the rhumb line to Fiji, and it sounded like a bizarre and risky place to visit; so, naturally, I wanted to go there.

"Let me get this straight," Kay said, "Now that we've lost the knotmeter and the satnav, you want to try to find a place that's under water, surrounded by a coral reef?"

"If we don't have a reliable fix when our worst-case DR says we're within five miles of South Minerva, we'll bear off for Fiji," I said, hoping to minimize her concerns. We were still 330 miles or more from South Minerva, the southernmost reef, so I knew I still had plenty of time to get my celestial house in order.

Scattered cumulus obscured half the sky at evening twilight. However, the seas were only a meter and the ten-knot southerly wind kept the clouds moving, enabling me to nail two shots each of Rigil Kentaurus, Canopus, Sirius, Spica, and Procyon. While Kay assumed the watch, I went below and plugged the numbers into the computer and waited for the J. Henry program to plot out my pinwheel for me.

The software enigmatically informed me my LOPs were too far out of bounds from my stated DR position to plot on the screen. What the heck? Muttering something unkind about damned modern conveniences, I took out a pad of universal plotting sheets and started plotting the LOPs so I could see them.

Instead of a five-star pinwheel I had something that looked like the last stages of a wild game of pick-up-sticks. If I had to choose a fix it could have been one of three different points, none of which agreed with my weak DR.

Going back through the numbers, it finally dawned on me: I had used the wrong date. We were in +12 time zone, and, when I added the ZT correction to the ship's local time of 1800, I forgot to advance to the next Greenwich date. Aha!

Revising the date was an easy change. The computer quickly recalculated the whole set of sights -- the blessings of modern technology!

That's better, I thought to myself as J. Henry began plotting out the fix on the screen. But my satisfaction was premature. Two of the sights agreed with the 1800 DR, three did not. I looked at my watch and wondered if I was going to get any sleep before my turn in the cockpit. Although I was not happy with the quality of the fix, I couldn't think of anything else that could be wrong with the data. I opted to call it a night hoping that morning stars would bail me out. As I curled up on the sea berth I wondered if maybe we ought to skip the Minervas and head for nice, big, high Fiji instead.

Morning stars were, for celestial purposes, non-existent. A 100% overcast had set in overnight dashing my hopes of establishing our whereabouts on the chart with better accuracy than "somewhere around here."

I waited all through the twilight period hoping for a quick shot through a hole in the clouds. My patience was rewarded with a meager bone: two quick shots of the moon's fading upper limb as it melted back into the cloud cover. After entering the moon sight numbers into the computer, I decided to check my timepiece against the radio while I waited for the calculation. I had just set my watch with the radio time tick the day before but, under the circumstances, I felt I might as well start re-checking everything.

It didn't surprise me when the seconds read 00 as the tone sounded. The watch was right on. But then a voice inside me said, "What time did he say it was?" I waited for the next minute to come around and this time listened closely to the familiar male voice cite the hours and minutes of Coordinated Universal Time. I couldn't believe it. I had set my watch exactly one minute off the correct time. A one-minute error in time is 15 miles of error in distance!

Once again, I re-ran the prior night's sights through the computer, but not before subtracting one minute from each of the their times. What a relief to finally see a decent fix appear on the computer's screen. It pleased me to the extent that I went to the trouble of plotting the LOPs on the chart rather than simply taking the latitude and longitude of the fix provided by J. Henry. Except for a disobedient Dog Star, I had a passable five-star fix that agreed closely with the DR position for the same time.

By noon the clouds had begun breaking up, permitting an observation of LAN, giving us a noon position of 27° 07' south, 177° 20' east, about 271 miles southwest of South Minerva.

At evening twilight we added Acrux to the crew of stars from the night before and this time almost got that pinwheel. Now we were in business -- if the weather would just hold until we made landfall (waterfall?, reef-fall?, what does one call it when there is no land?).

A suspicious, unforecast northwest wind began rising the next morning. On a close reach at six knots, we managed to find Antares, Achernar, Altair, Rigil Kentaurus, and the moon's upper limb through large gaps in the clouds. The fix showed Kavenga walking right up the rhumb line to South Minerva.

After another excellent six-star fix that evening, I confidently told Kay that we would sight South Minerva tomorrow morning about 0900 local time. "And if we don't?" she asked. "If we reach our fail-safe point where our worst case DR position puts us within five miles of South Minerva," I said, "and we don't have a good handle on our position, we'll give up and tack away to the west." I didn't want to put us in a situation where we were unsure of our position and not confident that we could tack safely to the west. If we hesitated and went beyond our fail-safe point, a danger would exist that we had passed South Minerva to the southeast. If we then tacked towards Fiji, we might accidentally find South Minerva the hard way.

The wind increased, necessitating the first reef in the main. We furled the 800-square-foot genoa, but unrolled it again later that night when our speed dropped.

By the 0300 change of the watch, the wind had piped up to 20 knots. The barometer had fallen five millibars from the prior evening's reading. I helped Kay furl the genoa and set the staysail before turning in until twilight. At 0500 I came on deck with the sextant to find a dark black squall overtaking us and threatening to eliminate the few remaining holes in the clouds that might allow me to get the sights we desperately needed if we were to safely establish our position before making our final approach on South Minerva Reef.

As the horizon became visible, the squall ran over us, bringing with it the classic wind shift and heavy rain. At 0545 the squall moved off and left us rolling uncomfortably in its wind hole. I caught a fleeting trace of Altair through the clouds and shot it three times before it disappeared. Another star, one I hadn't pre-calculated, peeped out long enough for one quick shot. Then Achernar joined the party and gave me what I thought was one good sight plus two questionable ones. Twilight ended, and I was about to head below when the moon popped out in a sliver of exposed sky. Bang, bang, bang; Kay recorded three sights for me, and I called it quits.

The resulting fix was ambiguous and disappointing. The Altair and Achernar LOPs were redundant, nearly on top of each other. They did show that leeway and current had taken us far to the right of track. The mystery star turned out to be Peacock, and its one line disagreed with the moon's averaged line. The result was a large cocked hat, ten miles on a side. I reluctantly marked the fix in the middle of the triangle. I then established our 0600 DR position based on the fix and an EP or estimated position at the closest point of the triangle to South Minerva Reef.

"It was a crummy fix," I told Kay as I came up the companionway. "We'll be at our fail-safe point in less than two hours."

"The seas are building, and there are more squalls coming, too," she said Kay, pointing to dark shrouds of rain astern of us to port and starboard. "Do you want to continue holding course?"

I breathed a sigh of defeat. I had really wanted to make this landfall, not only for the satisfaction of a celestial navigation landfall, but even more so for the chance to explore a small world in a remote part of the Pacific that exists exactly at the interface between the ocean and the sky above, with no permanent land above water and no recognized government to bow to.

"Let's continue steering for the reef until 0800. If we don't see anything by then, we'll bear off."

It was futile to keep going. At 0800 we'd still be just outside the fail-safe distance of five miles. I knew from our prior approaches to coral atolls and barrier reefs that we would be lucky, even with a heavy surf breaking, to spot the reef much beyond two miles.

Neither of us said anything as 0800 came and went. At 0805 I was about to trim the steering vane for a change of course to Fiji when Kay spoke up.

"That figures," she said.

"What's that?"

"Now the sun's coming out."

"Yeah, that's about par for the course," I said, thinking one sun line wasn't going to help much. Then I remembered the moon. My head snapped around to the bearing it had been on. It hadn't set yet! It was still 20 degrees or so above the horizon, visible through a fairly large hole in the clouds. I dove below for my sextant leaving Kay wondering what had got into me.

I handed her the sight log and shouted, "Stand by!" before even getting the moon down to the horizon. "Mark!," I shouted when the upper limb kissed the horizon the first time. Then twice more I shot it, taking more care with each one. The sun was easy, just slightly lower than the moon, but bright enough to give me a sharp lower limb against the serrated horizon. I moved over to the starboard side of the cockpit, wedging myself between the dodger and the gunwale. In exactly 100 seconds I had three solid sights of the sun.

I grabbed the sight log from Kay and hurried down the companionway to the nav station and began plugging in the times and numbers for the sights. At 0815, I had a good sun/moon fix. We were still nine miles southwest of South Minerva. The one Peacock sight that had put us closer was bad. At the time, however, I didn't know that and couldn't disregard what it told me.

After plotting the fix, it occurred to me to give the radar a try. I didn't think I'd be able to pick up the surf break at that distance, but if there happened to be any sailboats anchored in the lagoon perhaps I might pick up a mast or radar reflector.

When I first turned up the gain on Kavenga's Furuno unit, all I saw was 360 degrees of fuzzy, snow-like sea return. I concentrated on the area to the right of the heading marker between seven and nine miles out. Either I was starting to see things or one little blip amongst all the sea return began looking a shade brighter than all the snowy blips around it. I put the range ring on the blip: eight miles. While I was watching the screen, a wonderful thing happened. I started seeing the unmistakable interference lines of someone else's radar, whipping out from the center of the scope.

I turned on the VHF and transmitted "Any vessel at South Minerva, this is the yacht Kavenga calling on channel 16."

"Kavenga, this is Arjumand, where are you?" a friendly male voice replied.

"Eight miles southwest and coming in. Do you have room for one more at South Minerva?"

"It's deep in here but there's plenty of room to swing, so come on in!"

The breaking surf appeared on the radar scope at a range of four miles. At two miles, we picked up the long white line with our naked eyes as well as four sailboat masts in a small cluster behind the breakers.

As we headed for the passage into the protected lagoon on the northwestern side of the figure-eight-shaped reef, we were in a jubilant mood -- victory was at hand. But the narrow pass is tricky. There is nothing above water for visual bearings or radar ranges. The chart indicated several large coral heads obstructing the pass. I wanted to be able to see them in order to pass them safely.

The overcast sky made the surface of the water an impenetrable steely gray. We would have to get very close to the coral heads before being able to spot them. Using the VHF, we talked to Arjumand and another boat, Free Spirit, as we lined up on the pass. When they told us we were at the entrance we squared around to 120 degrees magnetic and started into the pass. Kay took the helm while I conned from atop the bow pulpit, scanning for coral heads. I could see the bottom coming up and took one last look back at Kay.

It was fortunate that I did. A charcoal black squall was on the verge of overtaking us. We'd never make it all the way through the pass before it caught us and reduced the marginal visibility we had. Reluctantly, I shouted back at Kay to reverse course.

For an hour we paralleled the reef's outer edge, keeping the breakers in sight through the pouring rain. When the squall passed, another one appeared close on its tail.

"Enough of this crap," I shouted to Kay, "let's get our butts in there."

Kay increased the engine speed and lined us up for a second time on what we hoped was the pass. The chart led me to believe that if we could find and follow the edge of the reef on the starboard side of the entrance, the coral heads would all be to port. The water color went from black to gray to dark blue to turquoise. Coral heads rose up off the port bow. We dodged toward the reef to starboard. Suddenly the water became darker again. We were in. We'd made it. Thus ended a memorable passage and began 18 wonderful days exploring the amazing South and North Minerva reefs.

Although pleased with the landfall, I had to admit to myself that reliance on modern electronics had gotten me into some lazy habits. The events of the past few days reminded me that fate can always reach out, take away all your fancy toys and ask some simple questions: How fast are you going? What time is it? Where are you? To stay out of trouble, you better be able to answer them.

Having completed a three-year circumnavigation, Steve and Kay Van Slyke now live aboard their boat in Gig Harbor, Wash.


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