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    Re: Question to Frank
    From: Jim Thompson
    Date: 2005 Apr 22, 06:21 -0300
    -----Original Message-----
    From: Frank R
    Can you experiment with different types of lunars: ... shorter distances, longer distances...?:
    Jupiter has been a wonderful teacher this week for my first real lunars, and the sky has been spectacularly clear.  Frank's online calculator has been wonderful for instant feedback.  I am gradually working out the bugs in my manual "form" that is based on Frank's "Easy Lunar" method using the NA:
    http://jimthompson.net/boating/CelestialNav/CelestNotes/LunarDistances.htm . 
    but the rest of life keeps intervening.  Also still doing only backyard lunars using calculated altitudes instead of an artificial horizon to measure all 3 angles.
     
    April 16:
    hs 71d 13.8' (picked the 1 of 3 that felt best)
    LD error +0.2'
    Lo error +06.3'
     
    April 17:
    Green shades on moon and Jupiter
    hs 59d 08.9' (mean of 4, discarded one)
    LD error +0.5'
    Lo error +15.0'
     
    April 21:
    Green shade on moon only
    hs 08d 49.4' (mean of 5)
    LD error -0.3'
    Lo error -08.2'
     
    I see now how lunars are MUCH, much easier to take as LD decreases: far less bobbling.  But note that my accuracy and precision certainly did not improve last night, in spite of how easy it was to keep Jupiter on the rim of the moon, now that LD is so small.  The reason clearly is my optics, undoubtedly the biological ones.  I don't see Jupiter as a disc in the 6x scope, rather as a slightly sparkling point of light.  The moon's rim seems very sharp, however.  I'd love to set the sextant on a tripod, to check backlash and index error more precisely too.  Over the range of this very small sample, my results wandered 0.8'!

    Jim Thompson
    jim3 at jimthompson dot net
    www.jimthompson.net
    --------------------
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