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    Re: Averaging
    From: Fred Hebard
    Date: 2004 Oct 21, 07:13 -0400

    Bill,
    
    I haven't explored much of this parameter space, so there may be areas
    where I'm dead wrong, but...  as best as I can tell, the only time you
    will see significant (>0.1' of arc) systematic shift will be within 10
    minutes of meridian passage.  That's when you shouldn't average (or
    over long time periods).
    
    I don't know where these cautions about high altitudes arose.  They
    would be difficult to shoot, just for swinging the arc, let alone the
    distance.  But averaging seems fine, except at meridian passage.
    
    I know I dodged your question, but tried to answer the intent.
    
    Fred
    
    On Oct 21, 2004, at 1:05 AM, Bill wrote:
    
    > Thank you Fred,
    >
    > What do you consider to be the upper limit of systematic shift due to
    > averaging that is acceptable, or is that situational?
    >
    > Bill
    >
    >
    >> On Oct 20, 2004, at 7:09 PM, Bill wrote:
    >>
    >>> My question, is there a rule of thumb that might indicate when
    >>> averages are
    >>> acceptable and when not.  For example, for error of .4' or less (due
    >>> totally to systematic errors from averaging) difference between
    >>> latitude and
    >>> declination, plus altitude should exceed 60d (or any other number
    >>> that
    >>> the
    >>> gurus decide is reasonable?
    >>>
    >>
    >> Bill,
    >>
    >> I'm no guru, let me assure you, but as best as I can tell, as long as
    >> you're 10 minutes away from meridian passage, averages or a straight
    >> line are fine, regardless of declination and latitude.  This is for
    >> short periods, such as 5 minutes.
    >>
    >> Fred
    >
    
    
    

       
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