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    Re: Lunars: Jupiter's BIG.
    From: Fred Hebard
    Date: 2003 Dec 20, 15:03 -0500

    I reduced your data and plotted your lunar times against the time of
    observation, below.  The data look very nice; not as good as the lunar
    of that Australian explorer Kieran Kelly discussed a few months ago,
    but very good.  The line is a least squares fit of a straight line.
    Interestingly, I usually plot the raw distance against the time of
    observation and use the least squares fit to pick out a point for
    reduction.  In this case, I chose your first observation, which was out
    by 48 seconds.  I should have chosen the third or fourth observation,
    which, being in the middle, were closer to the fit of the line to the
    average of the observations.
    I think perhaps the old method of using the mean of the observations
    would be better than using a line of best fit, although plotting the
    data instantly tells one how good they are.  Using the mean, the time
    would have been out by 8 seconds, about 2 minutes of longitude.
    Obs#    time of observation    time from lunar        diff
    1       12/19/03 9:30:37       12/19/03 9:31:24        48
    2       12/19/03 9:33:31       12/19/03 9:34:28        58
    3       12/19/03 9:36:15       12/19/03 9:35:50       -24
    4       12/19/03 9:39:15       12/19/03 9:39:37        23
    5       12/19/03 9:43:30       12/19/03 9:43:35         6
    6       12/19/03 9:48:15       12/19/03 9:47:30       -45
    7       12/19/03 9:52:30       12/19/03 9:52:22        -7
    On Dec 20, 2003, at 3:53 AM, Frank Reed wrote:
    > When you shoot lunars with Jupiter, you soon discover that the giant 
    > planet has a visible semidiameter through a good sextant. The accepted 
    > practice is to split the planet -- you take it to the Moon's limb and 
    > place the disk of the planet as best you can with its center right on 
    > the limb so that the planet is split in half along the Moon's limb. 
    > That's do-able...
    > Fortunately, Jupiter is far enough away that parallax is no issue 
    > (it's always less than 0.04 minutes of arc for Jupiter).
    > If anyone's interested, here's a set of Jupiter-Moon lunars from last 
    > night taken with a reliable Plath sextant:
    > Index Correction: +0.7
    > Assumed Position: Lat = 41d 22N, Lon = 71d 57W
    > Temp: 30F. Pressure: Normal.
    > All Lunars are Jupiter-Moon-Far Limb. Times are EST (US Eastern 
    > Standard Time). Sights start at Greenwich Date 12/19/2003, 09:30:
    > 04:30:37,? 43d 49.5
    > 04:33:31,? 43d 51.1
    > 04:36:15,? 43d 51.7
    > 04:39:15,? 43d 53.7
    > 04:43:30,? 43d 55.7
    > 04:48:15,? 43d 57.6
    > 04:52:30,? 44d 00.1
    > Enjoy!
    > Frank E. Reed
    > [X] Mystic, Connecticut
    > [ ] Chicago, Illinois


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