NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Longitude by altitudes. was Re: How Many Chronometers?
From: Brad Morris
Date: 2009 May 14, 11:02 -0400
From: Brad Morris
Date: 2009 May 14, 11:02 -0400
And speaking of navigation and time.... For a very long time, I was puzzled by Dutton's recommendation to navigators that they obtain a split seconds watch. He described two second hands. One would continue to beat time, the other would pause and hold the time whilst it was recorded. I search far and wide for a "split seconds" watch of this type. I am very pleased to report to the list that such a watch should have the complication known as "rattrapante". When you search on eBay for this type of watch, you immediately get listings describing exactly what Dutton recommended. I somehow managed to obtain one. Am I ever pleased! The rattrapante chronograph I obtained holds not only the seconds, but the hours and minutes and tenths of a second as well. All of the hands are analog. I have set the rattrapante complication to GMT, while the normal analog watch is set to my local time zone. Upon observation, I reach with my left hand to my right wrist and press the button. Now the altitude and time correspond and can be recorded at leisure. I have been carefully rating the rattrapante against the USNO time, (202)-762-1069 here in the US. The rate is 0.200 seconds per day, when rated over the past 20 days. Each day, the USNO time is compared to the rattrapante, and the resultant error is recorded. Since the tenths of a second is the resolution, I should continue more than 50 days to eliminate any quantizing error. If the rate is not precisely 0.2 seconds, then as the accumulation of short or long rate continues, eventually, there will be an advance or retreat that holds. I thought it relevant to report the name to others who might wish to obtain the watch recommended by the US Navy for celestial navigation. Dutton, after all, was the text used at the Academy! Best Regards Brad -----Original Message----- From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of frankreed@HistoricalAtlas.com Sent: Thursday, May 14, 2009 9:56 AM To: NavList@fer3.com Subject: [NavList 8259] Re: Longitude by altitudes. was [NavList 8178] Re: How Many Chronometers? Peter, you wrote: "Speaking of straw-man arguments.. This would seem to be an irrelevant distraction, Frank, introduced to cloud the issue." And you wrote: "Frank, your central argument is parading itself about in public while wearing no clothes. It is not a good look. Be a good chap and cover yourself up" And you wrote: "Do you just make up this stuff as you go along?" And you wrote: "similar opinions to yours with no basis at all for their suppositions (and that were, incidentally, self-serving, just like yours)." Thanks, Peter. Fascinating points, as always. -FER "Confidentiality and Privilege Notice The information transmitted by this electronic mail (and any attachments) is being sent by or on behalf of Tactronics; it is intended for the exclusive use of the addressee named above and may constitute information that is privileged or confidential or otherwise legally exempt from disclosure. If you are not the addressee or an employee or agent responsible for delivering this message to same, you are not authorized to retain, read, copy or disseminate this electronic mail (or any attachments) or any part thereof. If you have received this electronic mail (and any attachments) in error, please call us immediately and send written confirmation that same has been deleted from your system. Thank you." --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---