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On Jun 7, 2008, at 12:34 PM, FJones wrote:

> Does anyone on the list use navigation calculators?  If so, which
> model?

I use the current line of HP programmable calculators, the HP-48/49/50
series.  I have programmed them myself using their built-in RPL
language.  They have very long battery life and excellent numeric
accuracy.  Models can be bought for a little over $100 US I believe.
The learning curve for the RPL language is a bit high but it pays off.

Here is my celestial navigation program in RPL.  If you know how to do
it, you can download this ASCII text into any HP-48 or HP-49 or HP-50
calculator and you will have a directory with various buttons defined
to calculate the position of the sun, enter sextant angles, and
determine position.  It contains a long-term almanac and sight-
reduction tables.  It uses a lot of RPL built in functions that can do
unit conversions, polynomial evaluation, root finders, graphing, etc,
hence it is remarkably compact.  (ANA stands for Anacortes, WA where I
used this program a lot.)  I am afraid I can offer no other
documentation - you will need to learn RPL and just read the code to
see what it does.  -- Dan

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%%HP: T(3)A(D)F(.); DIR ANA \<< 48.502 'LAT' STO 122.603 'LONG' STO 8
'TZ' STO DATE TIME OVER OVER TSTR 5 24 SUB ROT ROT CALC ALT "ALT" \-
 >TAG AZ "AZ" \->TAG \>> NB \<< 47.48 'LAT' STO 121.7975 'LONG' STO 8
'TZ' STO DATE TIME OVER OVER TSTR 5 24 SUB ROT ROT CALC ALT "ALT" \-
 >TAG AZ "AZ" \->TAG \>> SEXTANT \<< "DATE mm.ddyyyy" DATE \->STR
INPUT OBJ\-> "TIME hh.mmss" "" INPUT OBJ\-> CALC "HT ft" "" INPUT OBJ\-
 > .3048 * \v/ -.0293 * "ANGLE:" "" INPUT OBJ\-> + DUP DUP DUP 4.4 +
7.31 SWAP / + TAN -.0167 SWAP / SWAP COS .0024 * + + 16 60 / + ALT -
'60_nmi' * \>> AH \<< "DATE mm.ddyyyy" DATE \->STR INPUT OBJ\-> "TIME
hh.mmss" "" INPUT OBJ\-> CALC "ANGLE:" "" INPUT OBJ\-> 2 / DUP DUP DUP
4.4 + 7.31 SWAP / + TAN -.0167 SWAP / SWAP COS .0024 * + + ALT -
'60_nmi' * \>> SNSET \<< 0 'T348' STO \<< DATE T348 DUP 1 DISP CALC
ALT \>> 'T348' { 15 21 } ROOT HMS\-> \->HMS 'T348' PURGE \>> EQT \<<
\Ge 2 / TAN SQ \-> y \<< L 2 * SIN y * M SIN 2 * E * - 2 L * COS M SIN
* 4 * E * y * + L 4 * SIN y SQ * 2 / - M 2 * SIN E SQ * 5 * 4 / - R\-
 >D \>> \>> CALC \<< HMS\-> TZ + \-> D t \<< 1.012 D DDAYS t 12 - 24 /
+ 36525 / 'T' STO [ .0003032 36000.76983 280.46646 ] T PEVAL 360 MOD
'L' STO [ -.0001537 35999.05029 357.52911 ] T PEVAL 360 MOD 'M' STO
[ -.0000001267 -.000042037 .016708634 ] T PEVAL 'E' STO [ -.000014 -.
004817 1.914602 ] T PEVAL M SIN * [ -.000101 .019993 ] T PEVAL M 2 *
SIN * + .000289 M 3 * SIN * + 'C' STO L C + '\Gh' STO [ .001813 -.
00059 -46.815 84381.448 ] T PEVAL 3600 / '\Ge' STO 125.04 T 1934.136 *
- '\GW' STO \Gh .00569 - \GW SIN .00478 * - '\Gh' STO \Ge .00256 \GW
COS * + '\Ge' STO \Gh COS \Ge COS \Gh SIN * R\->C ARG 360 + 360 MOD
'\Ga' STO \Ge SIN \Gh SIN * ASIN '\Gd' STO [ -2.58331180573E-8 .
000387933 0 280.46061837 ] T PEVAL T 36525 * 360.985647366 * + 360 MOD
'GST' STO GST LONG - \Ga - 'LHA' STO LAT SIN \Gd SIN * LAT COS \Gd COS
* LHA COS * + ASIN 'ALT' STO LHA COS LAT SIN * \Gd TAN LAT COS * - LHA
SIN R\->C ARG 180 + 'AZ' STO \>> \>> LAT 48.502 LONG 122.603 TZ 8 AZ
255.17798638 ALT 12.7522638832 LHA 70.540901144 \Ga .000618856 \Gd
2.68316750856E-4 \Gh 360.00067452 \Ge 23.4400413709 T 3.21571982661E-2
L 358.15035347 \GW 62.8436051744 M 75.15770741 E 1.67072820768E-2 C
1.86026412241 GST 193.14452 ETG \<< CL\GS 1 12 FOR i i .012003 + 0
CALC EQT \GS+ i .152003 + 0 CALC EQT \GS+ NEXT BARPLOT \>> END

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