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Make sure you go to the July 23 post not the July 25 or July 30
posting.

http://groups.google.com/group/NavList/browse_thread/thread/a270bc3d6aeb66d4?hl=en

gl

On Jan 6, 12:48�pm, glap...@PACBELL.NET wrote:
> You don't have that exactly right, the LOP moves westward one minute
> of arc every four seconds, not one nautical miles. Since the length of
> one minute of longitude varies as the cosine of the latitude the
> distance the LOP moves also varies by the cosine of the latitude. At
> the equator the length of one minute of longitude is one nautical mile
> but at 60� latitude it is only one half of a nautical mile.
>
> In addition to this, the amount of change in altitude also varies with
> the sine of the azimuth so you have to combine these two factors. Go
> to :
>
> http://navlist.googlegroups.com/attach/c09c132c9a92fad1/HO+249+extrac...
>
> which contains two tables called "motion of the body" or "M.O.B."
> tables that are used in flight navigation to allow for the motion of
> the body. Look at the table for four minutes. Since four minutes of
> time is 60 times four seconds of time just divide the tabulated values
> by 60 to obtain the change of altitude in four seconds of time. (Or
> you can just consideer the tabulated values as seconds of arc.)For
> example, the first value listed is 60' for latitude zero and azimuth
> 90�. Go accross the top line to 60� latitude and you will find that
> the change in altitude is 30' exactly one half of the change at the
> equator and which would result in a change of 30 NM in the intercept.
>
> Go to my July 30, 2008 post on the "Celestial up in the air" thread
> for further explanation at :
>
> http://groups.google.com/group/NavList/browse_thread/thread/a270bc3d6...
>
> gl
>
> On Jan 6, 12:20�pm, "Federico Rossi" 
> wrote:
>
> > Lu,
>
> > If I�ve understood well, this error doesn�t depend on your latitude on
> > earth, i.e. it�s a maximum of 1 nm for every 4 seconds (for bodies due east
> > or west) whether you are on the equator or far from it, does it?
>
> > Federico
>
> > Da: NavList@fer3.com [mailto:NavList@fer3.com] Per conto di
> > Lu Abel
> > Inviato: marted� 6 gennaio 2009 20.05
> > A: NavList@fer3.com
> > Oggetto: [NavList 6941] Re: Chronometer Suggestions
>
> > Irv and Bill:
>
> > It's a MAXIMUM of 1 NM for every 4 seconds, not a minimum. �
>
> > If the body you're sighting is directly north or south of you, even a fairly
> > significant time error would result in a very minimal shift in the LOP
> > produced by the body (the extreme example is Polaris). � On the other hand,
> > if the body you're sighting is directly east or west, then it's Geographic
> > Position is moving by 1 NM every four seconds and any LOP developed from
> > that sight would be off by 1 NM for every four seconds of clock error.
>
> > Lu Abel
>
> > Irv Haworth wrote:
>
> > Minimum of 1 NM for every 4 seconds..( a quick answer)..
>
> > Irvin F Haworth
>
> > W, Van BC Canada
>
> > � _____ �
>
> > From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf
> > Of William Sellar
> > Sent: January 6, 2009 5:05 AM
> > To: NavList@fer3.com
> > Subject: [NavList 6931] Re: Chronometer Suggestions
>
> > As a beginning celestial navigator, I am wondering how much time and watch
> > accuracy is actually required for practical navigation. �Can we predict how
> > many miles off one would be for every second of time error?
>
> > Bill
>
>
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