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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Leap second today
From: Brad Morris
Date: 2012 Jun 30, 15:04 -0700
From: Brad Morris
Date: 2012 Jun 30, 15:04 -0700
The purpose of the leap second is to adjust UTC to the subtle variations in the earth's rotation.
Time is adjusted such that the position of observable celestial objects (like pulsars) correspond.
But, the NA is simply an independent / dependent table. Entry into that table with the "correct" time will yield the "correct" celestial coordinates for the object tabularized.
On Jun 30, 2012 5:45 PM, "bill" <billyrem42@earthlink.net> wrote:
On 6/30/2012 4:52 PM, Gary LaPook wrote:
If, as is the normal case, you are only working your sights to the
precision of of one second of time, then you make no change and the NA
is always right to this level of precision. This change will result in a
change of the GHA by 0.25 minutes which is de minimus at this normal
level of precision. If you are a perfectionist then you have always made
the corrections of the tenths of a second broadcast on WWV so you will
just go on doing the same thing except the value you use will change
from the current plus 0.6 seconds to a minus 0.4 seconds. When you apply
these corrections properly there will be no change in the GHAs.
I thought I might look to the GHA of Aires in the daily pages of the NA for confirmation that they do not add a leap second to the tables, but 1 s is a little below its resolution. The GHA of Aires usually toggles back and forth between an increase of and 0d 59!1 and 0d 59!2 change within a 24 hour2 over a two-day period.
There is no indication of that pattern being broken around June 30th, until it reaches the difference between 0 hours July2 and 0 hours July 4, where the difference remains 0d 59!1 for two consecutive days. Given the resolution that is evidence of nothing more than rounding, so no help there.
Bill B
