Night vision unit expands celestial nav window
Just before the Marion-Bermuda Race, I remembered that Firefly, Patrick Wilmerding's J-42 on which I had enlisted as navigator, had an ITT Night Mariner monocular on board. Thinking it might be fun to experiment with taking celestial sights in the middle of the night, I ordered a sextant/monocular bracket from John Luykx at InfoCenter (Forestville, Md., 800-852-0649) and barely listened as he explained how to compensate for semidiameter while bringing down a star using night vision equipment. Little did I know how happy I'd be later that we had the equipment ready to go.
Standing a watch and navigating during the race turned out to be a lot for me to handle even though the weather was fine and the sailing smooth. We had eight in the crew and only four bunks, so there was no sneaking down below for a navigator's nap during watch. I didn't get much sleep the first night out (Friday) and slept through morning stars, managing just a moon line after twilight had passed. I got running fixes of the sun all day. Twilight sights were a problem again; I only was only able to shoot Venus between the clouds.
So, it was 0245 Sunday morning and we were nearly all the way across the first major feature of the race, a small but powerful warm eddy, when Michael Wilmerding reminded me of the Night Mariner. I was dubious. After all, if this thing were any good, wouldn't everyone else in the race be using one too? I had never heard of anyone using it in the race before. And besides, I was pretty comfortable with a day's worth of running fixes.
But it happened to be one of the first clear skies of the race, and the stars were out. Using the nightscope, I shot three sights each of Schedar, Alkaid, and Arcturus. The horizon, appearing green on the Night Mariner, seemed pretty clear and visible, if a little artificial looking. The resulting fix looked to be the best of the whole race for me. All three shots of each star were on top of each other and the sights plotted nicely right on the DR track.
I remained suspicious, but a couple of hours later I shot the moon and Vega conventionally at dawn. They too were right on the DR track, corroborating the Night Vision sights. An evening later, I used the Night Vision to shoot Alkaid and Deneb, and that sight was right on the money as well.
Taking sights in the middle of the night was easy and fun. The stars are very bright at that point, and it's easy to identify them. However, I found that I often could see two or three stars at once in the index mirror (I used a split mirror) in addition to my target star. This created the risk of actually using the wrong one at the critical moment. Semidiameter did not turn out to be much of a problem. John Luykx suggests using the center of the star on the horizon rather than the lower limb of the somewhat enlarged and fuzzy images. I just fudged on that, and it seemed to work. Ironically, peering into the Night Mariner ruined my night vision, as the greenish image is really bright.
Another demonstration of the power of the Night Mariner occurred the first night out. I spotted seven boats with my naked eye. Using the Night Mariner, I could see 24 masthead lights. Visibility was a little hazy, but the Night Mariner cut through it well.
My conclusion is that I would be delighted to have Night Vision on board during the next Marion-Bermuda Race. It made taking star sights easier, and the results seemed excellent.
Alex Agnew, in addition to being an offshore navigator, is Ocean Navigator's advertising director.