NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant accuracy and possibility of future improvement
From: Lu Abel
Date: 2016 Jul 21, 18:03 +0000
From: Lu Abel
Date: 2016 Jul 21, 18:03 +0000
I believe a much more useful discussion would be to remember WHY we are taking sextant shots -- to determine our position -- and then talk about how to improve that process.
What would be more useful in achieving position fixing via a sextant -- a highly precise artificial horizon or better sight reduction?
Imagine, for example, a sextant equipped with electronics to completely automate the process of logging sights. I take a sight and instead of shouting "mark" to an assistant who then records time and waits for me to read the sextant, I press a "mark" button on the sextant and the arc reading and time (from an electronic chronometer) are automatically recorded in the sextant's memory. With some simple additional inputs (body observed, HE, DR position), the sight is automatically reduced (Stan Klein's Celestial Tools program is a wonderful example of electronic sight reduction, it even has a built-in Nautical Almanac and could easily be implemented in a microprocessor built into my hypothetical sextant).
Which would a real-world navigator rather have -- a sextant such as envisioned above or one with a arc-second-accurate artificial horizon. Yes, "both of the above" could be an answer, but I'm challenging priorities.
From: Robert Eno <NoReply_RobertEno@fer3.com>
To: luabel@ymail.com
Sent: Thursday, July 21, 2016 10:28 AM
Subject: [NavList] Re: Sextant accuracy and possibility of future improvement
And here I thought I was a die-hard astro-nav enthusiast.
I stand by my earlier comments on this topic regarding economics and the advent of small, pocket-sized GPS receivers as the reason why improvements were never made to the hand-held sextant.
Many of you brought up the valid point about tremors in the human hand being the main reason why it would be futile to try to improve the accuracy of an already precise angle-measuring device.
But Paul Dolkas has, in my opinion, it the nail squarely on the head. As one who cut his teeth taking sextant observations on land (and before the advent of GPS) , I always believed that the next major improvement to the sextant was to find a more reliable and accurate means of finding the horizontal. I own a mint-condition C.Plath bubble attachment with the adjustable bubble, which is a fairly precise instrument with lots of practice. And the RAE MK IX aircraft bubble sextant is, in my opinion the best bubble horizon system ever invented. That being said, bubble horizons are fickle and they too, are subject to the vagaries induced by natural hand tremors. I swear there have been times where the bubble was actually mimicking my heartbeat.
Anyway......I would love to see some kind of device such as what Paul has described, and that would clip into where the telescope is mounted -- much like a bubble attachment.
Had GPS not come onto the scene, I believe that sextant development would have gone in this direction.
But again, it gets down to economics and right now, I suspect that there simply is not a market to make the development and production of such a device economically viable. That being said, throw in a major military threat to the GPS system and the US DOD will probably come up with something if they have not already done so on the QT.
Robert
