Shooting Stars

7 May

May 5, 2019/Day 212

Miles since departure: 28,667

Avg. Miles/Day: 135

 

Six days over 160, and we’re still cranking.

I’ve been at astronav consistently since rounding up into the Atlantic forty six days ago, and yesterday marks a turning point.

Yesterday, I switched off the chart plotter.

The sextant I use is the Celestaire Astra IIIB. I bought it in 2005 from my local chandlery because it was the only sextant they sold. Not the only brand; there were no others in the store. I was about to make my first ocean crossing and wanted to learn celestial enroute but lacked the basic tools. This sextant looked like serious business and came in a lovely mahogany box and wasn’t too expensive. So I bought it without further ado and have been using it on passages ever since with great success.

With one exception. Stars.

Star sights are typically taken during morning and evening twilight, when the higher magnitude bodies begin to appear but the horizon is still visible. And I have tried often at sea to shoot stars during this time. I’ve done well when I can find the damned target, but that’s the tough part. Stars can be very dim.

The Astra IIIB came with what’s called a Whole Horizon Mirror (sitting next to the sextant in the photo). This is a coated lense that allows the user to see the whole ocean horizon with the image of the body (sun, moon, or star) superimposed onto his field of vision in its entirety. This lense is excellent for bright objects and makes “racking down the sun” a breeze.

But I found that the coatings on the lense applied just enough shading that seeing stars was difficult. To be fair, there are other factors, one of which is that I wear bifocals; another is that Mo is rarely a stable platform from which to find a pinprick of light in the heavens.

When I broached this issue with Celestaire, Ken Gebhart immediately recommended I try the Traditional, split mirror (attached to the sextant in the photo). This is the technology that every sextant employed before coated lenses were invented. And one benefit of the Astra IIIB is that it is designed to facilitate easy mirror swaps.

The split mirror is just as you’d imagine. Half the lense is mirrored and half the lense is clear. Thus, half of the image one is seeing is unadulterated horizon and half is of the sky in which resides the body being racked down. This playing halvsies with the image can take some getting used to and is a bit more difficult on a bounding boat, but there is no shading on this mirror.

And this has made all the difference for me. Now the stars I pursue are as bright in my scope as they are with the naked eye. For a couple weeks I’ve been shooting both sun and stars with the split mirror and feel I’ve made the transition.

Having, now, better access to stars, planets, and the moon means that I can get two or three widely separated (morning, noon, and evening) fixes on a day with good visibility, and this has been encouragement to take the next step.

It has dawned on me only slowly that the sextant work is the easy part. What’s hard is keeping track of one’s position in the interim; that is to say, dead reckoning. This moment-to-moment knowing is something that the chart plotter does with such ease, that unless it’s decommissioned, one has no incentive to get to know the compass or the log. Why learn to like oatmeal if someone delivers strawberry waffles to your bedside each morning?

So, it’s off. And I’m not lost. I don’t think…

To be honest, it’s not entirely off. The chart plotter is my AIS interface, and I still want the noon-to-noon mileage numbers, so the screen is off while the unit runs in the background. And I am relearning the mysteries of variation and deviation.

This article was syndicated from The Figure 8 Voyage

Comments

  1. Maes Jan Jaap

    The most important thing when using the sextant is your telescope magnifier to focus on a star. Then leave the sextant in its angle look at the azimuth take time with a chronometer go inside nice and slow look at the gps time gmt and take time and your chrono offset on paper. The more you practice you will see that those preselected catalogues are not useful on a cloudy day. That is when you shoot between the stars. Do not use the Moon as she is too close to Earth and does not give good results. Enquiries: maesjanjaap@gmail.com

  2. Scott Michaels

    Interesting article. I just recently decided to get a sextant as backup to my GPS and wanted to learn a new skill. I purchased the same sextant, Astra IIIB, lightly used on eBay. I really went native and purchased a Taffrail Log too in case all my electronics go out. Now, I just need to find the time to go cruising!

  3. Kenneth Simon

    No Lat/Lon position today? I have been plugging your positions into INavx.
    I assume you are using Pub 249, Volume 1, “Selected Stars,” which will give you the positions of seven stars, with three highlighted for max separation, just find your approximate position in the tables within a couple degrees. Set your sextant on the Hc of the star, then point it at the heading in the Zn column, and there is your dim star in twilight that you couldn’t see before.

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