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Re: polaris dec
From: Greg R_
Date: 2006 May 19, 12:31 -0700
> Just as a note, 1 arcminute equals 1 nautical mile. Greg has
the
> calculation right however.
>
> On May 19, 2006, at 1:41 PM, Greg R. wrote:
>
> > Hi Greg (what's that echo in here?.... ;-))
> >
> > If you're asking why the declination of the (suppposed) pole star
> > isn't
> > exactly 90 degrees - well, that's because it really isn't.
> >
> > Polaris is close to having a 90°N declination, but it isn't exact
> > and it's
> > off by enough to throw off your navigtion calculations by several
> > miles.
> > Remember that 0.1 degree = 1 NM, so 60' - 18' = 42 NM - not exactly
> > what I'd
> > call "accurate" navigation, but probably close enough to help get you
> > oriented if you're *totally* lost somewhere... ;-)
> >
> > --
> > GregR
> >
> >
> > ----- Original Message -----
> > From: "cfi@licfi.com" <cfi@LICFI.COM>
> > To: <NAVIGATION-L@LISTSERV.WEBKAHUNA.COM>
> > Sent: Friday, May 19, 2006 9:53 AM
> > Subject: polaris dec
> >
> >
> >> Question for the list:
> >>
> >> Please excuse the neophite question but; Why does the USNO on-line
> >> almanac show the following?:
> >>
> >> declination of polaris:
> >> month d m
> >> may 89.17.5
> >> june 89.17.4
> >> july 89.17.3
> >> aug 89.17.3
> >> sept 89.17.4
> >> oct 89.17.6
> >> nov 89.17.7
> >> dec 89.17.9
> >> -------2007------
> >> jan 89.18.1
> >> feb 89.18.1
> >> mar 89.18.1
> >> apr 89.18.0
> >> may 89.17.8
> >> june 89.17.7
> >> july 89.17.6
> >>
> >> Thanks,
> >> Greg
> >>
> >>
> >> --------------------------------------------------------------------
> >> mail2web - Check your email from the web at
> >> http://mail2web.com/ .
> >>
>
From: Greg R_
Date: 2006 May 19, 12:31 -0700
Fred wrote:
> Just as a note, 1 arcminute equals 1
nautical mile. Greg has the
> calculation right however.
> calculation right however.
Fred is technically correct - I took a "shortcut"
(and maybe some liberties as well...) with the terminology, something we
probably all do in practice. Thanks for keeping
me honest. :-)
--
GregR
----- Original Message -----
From: "Fred Hebard" <Fred@ACF.ORG>
Sent: Friday, May 19, 2006 12:07 PM
Subject: Re: polaris dec
> calculation right however.
>
> On May 19, 2006, at 1:41 PM, Greg R. wrote:
>
> > Hi Greg (what's that echo in here?.... ;-))
> >
> > If you're asking why the declination of the (suppposed) pole star
> > isn't
> > exactly 90 degrees - well, that's because it really isn't.
> >
> > Polaris is close to having a 90°N declination, but it isn't exact
> > and it's
> > off by enough to throw off your navigtion calculations by several
> > miles.
> > Remember that 0.1 degree = 1 NM, so 60' - 18' = 42 NM - not exactly
> > what I'd
> > call "accurate" navigation, but probably close enough to help get you
> > oriented if you're *totally* lost somewhere... ;-)
> >
> > --
> > GregR
> >
> >
> > ----- Original Message -----
> > From: "cfi@licfi.com" <cfi@LICFI.COM>
> > To: <NAVIGATION-L@LISTSERV.WEBKAHUNA.COM>
> > Sent: Friday, May 19, 2006 9:53 AM
> > Subject: polaris dec
> >
> >
> >> Question for the list:
> >>
> >> Please excuse the neophite question but; Why does the USNO on-line
> >> almanac show the following?:
> >>
> >> declination of polaris:
> >> month d m
> >> may 89.17.5
> >> june 89.17.4
> >> july 89.17.3
> >> aug 89.17.3
> >> sept 89.17.4
> >> oct 89.17.6
> >> nov 89.17.7
> >> dec 89.17.9
> >> -------2007------
> >> jan 89.18.1
> >> feb 89.18.1
> >> mar 89.18.1
> >> apr 89.18.0
> >> may 89.17.8
> >> june 89.17.7
> >> july 89.17.6
> >>
> >> Thanks,
> >> Greg
> >>
> >>
> >> --------------------------------------------------------------------
> >> mail2web - Check your email from the web at
> >> http://mail2web.com/ .
> >>
>
