NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Attempting to decipher a "time sight"
From: Stan K
Date: 2016 May 31, 18:55 -0400
From: Stan K
Date: 2016 May 31, 18:55 -0400
Frank,
You can thank (blame?) Ed Popko. If he were not trying to find a bug in his programmable calculator 19th century time sight program, I would never have noticed this typo. Ed solved his problem, which had nothing to do with the typo. Ed also pointed out a bug in my own 19th century time sight program. All of this prompted me to add an option to my program. Before the option it would calculate based on the entered values, including minutes of arc, etc. Now there is the option to only use tabular values. It is attached for your amusement.
Stan
-----Original Message-----
From: Frank Reed <NoReply_FrankReed@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Mon, May 30, 2016 5:55 pm
Subject: [NavList] Re: Attempting to decipher a "time sight"
Attached File:
Attached File:
From: Frank Reed <NoReply_FrankReed@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Mon, May 30, 2016 5:55 pm
Subject: [NavList] Re: Attempting to decipher a "time sight"
Stan, you wrote:
"I note that there is a typo in either Hart's original or your transcription. It shows the sum correctly as 19.37899. Half of this is 9.689495, so, to five decimal places, the half-sum should be either 9.68949 or 9.68950, but not 9.68849. The time shown of 3-54-16 is correct for 9.68949 (or so)."
"I note that there is a typo in either Hart's original or your transcription. It shows the sum correctly as 19.37899. Half of this is 9.689495, so, to five decimal places, the half-sum should be either 9.68949 or 9.68950, but not 9.68849. The time shown of 3-54-16 is correct for 9.68949 (or so)."
Thanks! I was curious enough to check, and it turns out the typo was in the original (I would have guessed it arose in auto-transcription, but that is so good these days...). I've attached below a screen capture from the original page with the section I quoted previously. I wonder if Hart got letters from attentive readers back then?!
Also I'm including a screen cap of another reference to a time sight in the same book which I discovered just now by searching on "secant" as a quick way to get to the page with the calculation. This one Hart intended for comedy. For us today it's yet another example of my claim that navigation was acceptable as "women's work" back then.
Frank Reed
Attached File:
Attached File:
File: 135486.timesight.zip
