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Re: Question to Frank
From: Jim Thompson
Date: 2005 Apr 22, 06:21 -0300
From: Jim Thompson
Date: 2005 Apr 22, 06:21 -0300
-----Original Message-----
From: Frank RCan 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:
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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