NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Swinging the arc: two methods, one preferred
From: Hewitt Schlereth
Date: 2011 Jan 6, 22:03 -0400
From: Hewitt Schlereth
Date: 2011 Jan 6, 22:03 -0400
Thank you, Paul -
It's been overcast here a lot lately too. In thinking about this technique further this afternoon, I now visualize it as analogous to inverting the sextant to bring the horizon up to a star. But then, instead of flipping the sextant back to "normal" you hold the scope on the star and rotate the sextant around the axis of the scope. Thus instead of swinging the star (sun, moon, planet) across the horizon, you swing the horizon around the body. Not all the way around, of course - that would require switching hands. Just enough to ensure no gap opens and that the body doesn't dig into the horizon.
Does that seem right? Anyway, it sounds pretty slick and if it's clear tomorrow, I'll try it.
Thanks again. Hewitt
It's been overcast here a lot lately too. In thinking about this technique further this afternoon, I now visualize it as analogous to inverting the sextant to bring the horizon up to a star. But then, instead of flipping the sextant back to "normal" you hold the scope on the star and rotate the sextant around the axis of the scope. Thus instead of swinging the star (sun, moon, planet) across the horizon, you swing the horizon around the body. Not all the way around, of course - that would require switching hands. Just enough to ensure no gap opens and that the body doesn't dig into the horizon.
Does that seem right? Anyway, it sounds pretty slick and if it's clear tomorrow, I'll try it.
Thanks again. Hewitt
On Thu, Jan 6, 2011 at 8:58 PM, Paul Hirose <cfuhb-acdgw@earthlink.net> wrote:
Hewitt Schlereth wrote:In my opinion rocking a sextand is one of those skills most easily learned by not attempting to think too hard. I went out this afternoon and shot the Sun (fairly low), and also a little cloud conveniently placed at a high altitude. Neither body was difficult to swing through the horizon, I wasn't conscious of using different movements for these bodies, and I couldn't begin to tell you how my rotation axis was oriented.
To take the sun as an example: when you have it at the right altitude,
does the horizon appear to slide around the edge of the sun's disk,
just touchng it; as it were, stroking it?
If you have a clear picture of the body remaining more or less centered as the horizon approaches (or passes through) then retreats, I think your hand will learn to make it happen without conscious effort. Perhaps the books err in attempting to tell you how to move the sextant instead of making clear what you should see in the scope. Or the imagery is confusing. Some diagrams show the Sun swinging back and forth as if it's at the end of a little pendulum.
--
