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    Re: Instrument Error
    From: Fred Hebard
    Date: 2005 Apr 24, 19:10 -0400

    Bill,
    
    Here are the data with the mean date and time, UT1, and the altitudes.
    The location was 36*46.8N, 81*50.7W.  The observation for 18 April is
    listed as for 17 April in the original table, where the separate dates
    are zone time rather than UT1.  Most of the the time the sun and moon
    are higher than 20* altitude.
    
    Fred
    
    Objects Mean(Date&Time) D       Sc      Mc      N(delarc')      Mean(delarc')   StdDev(delarc')
    Moon,Antares    23Sep2004 00:39:53      38      15      26      2       0.1     0.38
    Moon,Jupiter    18Apr2005 00:54:43      58      26      75      7       0.5     0.21
    Moon,Jupiter    20Apr2005 01:02:02      22      30      50      6       -0.1    0.28
    Moon,Venus      06Oct2004 11:34:59      49      35      80      7       -0.2    0.26
    Moon,Venus      07Oct2004 10:59:03      39      32      70      6       -1.1    0.23
    Moon,Sun        20Sep2004 22:06:58      80      15      26      6       1.2     0.37
    Moon,Sun        21Sep2004 21:11:26      93      25      17      6       1.3     0.49
    Moon,Sun        05Oct2004 17:13:14      98      48      12      6       1.4     0.15
    Moon,Sun        06Oct2004 15:55:08      87      41      40      8       1.2     0.34
    Moon,Sun        08Oct2004 14:45:46      66      35      66      10      0.7     0.38
    Moon,Sun        07Nov2004 15:27:00      63      31      51      6       1.7     1.28
    Moon,Sun        16Apr2005 22:03:24      93      23      62      6       1.4     0.15
    Moon,Sun        17Apr2005 20:18:11      103     44      31      8       1.2     0.24
    
    On Apr 24, 2005, at 6:42 PM, Bill wrote:
    
    > Fred
    >
    > I am envious of your standard deviations, especially with the larger
    > angles.
    > To date every Sun/moon I have shot had the Sun to the west of the moon
    > (April 13, 2005 and on), and I prefer separating, so did try some
    > set-and-leave shots for separation.
    >
    > What I find interesting is despite different methodologies, scopes,
    > instruments and locations we both wind up over shooting the target
    > consistently (and it would appear we both saw the same Sun and moon in
    > April
    > ;-)
    >
    > What time(s) of day did you make your April 05 observations?  As I
    > noted
    > before, while my STDEV's of error were horrible, the observations I
    > made
    > when the Sun and moon had Hc's over 40d turned out remarkably well,
    > with
    > mean errors in the 0.25' to 0.5' range.  The "easy" shots with the
    > moon high
    > in the sky and the Sun in the 15d-25d range all had sub 0.2' STDEV
    > error
    > means, but error means were in the 0.5' to 1.0' range.  Admitted the
    > instrument in in the hands of a novice, and I don't have enough data
    > points
    > to justify a firm conclusion, but it appears the lower the Sun gets
    > the more
    > I overshoot.  There is not enough flattening of the Sun by refraction
    > to
    > account for the trend.  If you are using Franks calculator, I recall
    > he did
    > have a correction for Sun/noon flattening, then disabled it.  I do not
    > know
    > if he has plugged it back in.  Either way flattening could only
    > account for
    > 0.1' or so.
    >
    > If memory serves, Alex had run test using the Sun for IE with both his
    > Galilean and inverting scopes, and saw little or no significant
    > difference.
    >
    > Still stumped
    >
    > Bill
    >
    
    
    

       
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