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Article: <5f71n6$rta@sjx-ixn6.ix.netcom.com>
From: saquo@ix.netcom.com(Nancy )
Subject: Re: IN SYMPATHY to the Hale-Bopp Cooperative
Date: 28 Feb 1997 16:39:02 GMT
In article <5f1u7b$19p0@news.ccit.arizona.edu> Jim
Scotti writes:
>> 5. Why did Brian Marsden try so damn hard to fit the
1993
>> McNaught image that he had to throw out 90% of the data
>> the public gave him in order to make it fit!
>> Nancy (saquo@ix.netcom.com)
>
> I can't say that 90% of the observations were thrown out,
but
> Marsden and any other orbit computers always remove
> obviously errant observations in order to improve the fit.
> Now before you ay that that implies that the orbits are
> "cooked", I can speak for all observers in saying
that
> occasionally you make a measurement which for whatever
> reason does not fit - perhaps a field star is in the way, or
> the reference star catalog has large errors (as some that
> we use are known to have). Also, inexperienced observers
> sometimes measure the wrong part of a comets often
> busy image.
> jscotti@LPL.Arizona.EDU (Jim Scotti)
(Begin ZetaTalk[TM])
Occasionally? Marsden stated he reduced the available data by a
factor of 10, taking only 10% of it, in order to make McNaughts
1983 image fit. It was a predetermined orbit, and only the data
that would support that predetermination was allowed to be
included! We don't look at the data and THEN arrive at a
conclusion? We have a conclusion and the data is included
selectively, based on the predetermination? This is SCIENCE? How
does he KNOW if an amateur recorded the wrong part of what was
supposed to be a comet? He gets their coordinates!
(End ZetaTalk[TM])
........
Comment on the 1993 Observation of C/1995 O1
(Hale-Bopp), by Brian G. Marsden
21 January, 1996
The problem with fitting the comet's orbit seems to be that the excess weight of the 1995 data (more than 700 observations) can throw a large residual into the single 1993 position, presumably because of systematic errors in the GSC reference-star system. By substantially reducing (e.g., by a factor of ten) the relative weight of the 1995 data, it is possible to fit the 1993 position completely satisfactorily.
..........
ZetaTalk
1995 October 25
Conspirators have also lined up images of Hale-Bopp to give the impression of a carefully plotted orbit. Those images which would show the orbit points plotted on empty space have been excluded. Where bright parts of the exploding star Hale-Bopp happen to line up with the orbit, these images they have retained.