NavList:

Stan, you wrote:
"What am I doing wrong here? I must be overlooking something."

Long, long ago, some EIGHT-SEVEN lunations ago... we went over this very issue in NavList messages --and by "we", I mean literally "you and I"! In any case, the reason that the augmentation is not explicit is because it cancels out in this correction if you do it in the right order. As I wrote in July 2006, "If you do the SD correction after the parallax, the augmentation cancels out." Here's some "basic" code to reproduce the tables in the back of the Nautical Almanac:

begin
'Get actual HP for this case:
input(HP)
'Get observed altitude, h1, for this case:
input(h1)

'Define kk=180/pi for angular conversions:
kk = 180/3.141593
'Define Moon's mean HP for these tables:
HP0 = 57.7

'SDcon is the ratio of the Moon's mean SD to HP0. A ratio of 0.2724 would
'perhaps be more accurate but this value matches the tables:
SDcon = 0.2711

'SD0 is the semi-diameter at the mean Horizontal Parallax, HP0:
SD0 = SDcon*HP0

'Correct for refraction.
'refr0 is a function to calculate refraction (in minutes of arc)
'or take it from pre-defined tables ("stars and planets" values in NA):
h2 = h1 - refr0(h1/kk)/60

'Add in parallax in altitude and mean semi-diameter:
h3 = h2 + HP0 * cos(h2/kk)/60 + SD0/60

'The Lower Table uses the average altitude from the upper column:
havg = 2.5 + 5*int(h1/5) '"int" here is equivalent to "floor" function

'h4 (LL, UL) is the increment in the Moon's semi-diameter and
'its parallax for the difference between the actual HP and the mean
'Horizontal Parallax, HP0.
dHP = (HP - HP0)/60
dSD = SDcon*dHP
h4 = h3 + dHP*cos(havg/kk)
h4LL = h4 + dSD
h4UL = h4 - dSD

'To keep the Lower Table corrections always positive, add
'5 minutes of arc to the LL correction and 35 to the UL correction.
'To compensate, subtract 5 minutes of arc from the Upper Table.
'Also subtract twice the mean semi-diameter for the UL.
UTcorr = 60*(h3 - h1) - 5
LTcorrLL = 60*(h4LL - h3) + 5
LTcorrUL = 60*(h4UL - h3) - 2*SD0 + 35

output(UTcorr, LTcorrLL, LTcorrUL)
end

I haven't tested this today, but it worked seven years ago! :)

-FER

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