NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2010 Feb 18, 11:09 -0500
Hi Bill
I stand corrected!
I will estimate my index error using the described method (upper and lower limbs of the sun) and report back.
Best Regards
Brad
From: navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com]
On Behalf Of Bill Morris
Sent: Wednesday, February 17, 2010 3:21 PM
To: NavList@fer3.com
Subject: [NavList] Re: Reliable Index Correction to a Tenth Minute of Arc; WAS Longitude by lunar altitudes
Brad
You wrote:
"As to the recalled difficulty with different telescopes, I would suggest that this implies a lack of parallelism between the plane of the arc of the instrument and the long axis of the telescope. "
I think I am correct in saying that as the sextant reading approaches zero, so does the error from mis-collimation reduce. At a reading of 10 degrees, for example, Simms gives the error as only about 5 seconds for a tilt of a whole degree (an amount that
should be noticeable to most people).
I suggest that those who believe they can correctly estimate their index error to a tenth of a minute on the basis of a single estimate deceive themselves. I would invite them to estimate it thirty times in a row and if they can get the same result within
a tenth of a minute each time, I will be among the first to congratulate their instrument.
Kind regards
Bill Morris
Pukenui
New Zealand
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