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    Re: How far is polaris?
    From: Gary LaPook
    Date: 2007 Nov 22, 23:05 -0800

    Gary adds:
    Look at my September 29th post in the sight reduction tables topic for
    more information on sight reduction.
    On Nov 22, 11:01 pm, glap...@pacbell.net wrote:
    > Gary writes:
    > No, it accounts for the apparant movement of Polaris due to the
    > changing position of the earth's pole.
    >  If you look in the Almanac you
    > find that the positions of the stars change during the year.
    > Most of the change of coordinates of  the stars published in the
    > almanac
    > are not due to the stars' proper motions but are due to a change in
    > the
    > coordinate system used to define the stars' positions, a coordinate
    > system that changes with the earth's movement. The zero point of the
    > stellar coordinate system is the vernal equinox. Since the earth is
    > precessing and wobbling on its axis this zero point moves along with
    > it
    > making it appear that the stars have moved. Since the earth completes
    > on
    > cycle of precession every 26,000 years, the vernal equinox moves eight
    > tenths of a minute of arc every year and this accounts for most of the
    > changes seen in the stars' coordinates.
    > On Nov 22, 1:39 am, Isonomia  wrote:
    > > In other words, A2 accounts for the finite distance of the star! That
    > > is to say, the star wobbles with respect to the background galaxies
    > > (can't say stars because they are too near!!!)
    > > It is absolutely mind boggling to think that a handheld instrument
    > > like a sextant could possibly be affected by the distance to the
    > > stars.
    > > It completely turns history on its head. I've always been led to
    > > believe that astronomers looked at the stars as an end in itself - the
    > > great scientists pushing back the frontiers of knowledge  - knowledge
    > > for the sake of knowledge's sake!
    > > In fact, it seems to me that knowledge of the stars and motion of the
    > > planets was a necessary but fairly god-forsaken task mainly undertaken
    > > as a part of the production of accurate navigation tables.
    > > Engineers produced the equipment necessary to take the measurements,
    > > engineers then took the measurements and then some self-publicist
    > > scientist came along took what was already known by the engineers and
    > > gave it a grand title of the grand theory of space, etc. and claimed
    > > it was entirely his work!
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