# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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From: Dan Allen
Date: 1999 Mar 16, 12:28 EST

```You can easily program in the sight reduction formula into an HP19BII or any
other HP calculator with HP Solve.  This is, of course, just the law of
cosines:
Spherical Trig Law of Cosines
cos(a)*cos(b) + sin(a)*sin(b)*cos(ab) = cos(c)
and then you can use it to solve both great circle distance calculations and
sight reduction by the following use of a, b, ab, and c:
For Great Circle Distance Computations:
a = 90 - lat1, b = 90 - lat2, ab = lon2 - lon1: c*60 = distance in nmi
b = c, c = b, recalc and ab = inital course
For Celestial Nav Sight Reduction:
a = 90 - estLat, b = 90 - decl, ab = LHA = GHA - estLong, 90-c = altitude
b = c, c = b, recalc, and ab = azimuth (360-az if lha < 180)
Dan
-----Original Message-----
From: Titanium Tom [mailto:titom@XXX.XXX]
Sent: Friday, March 12, 1999 7:29 PM
To: Daniel K. Allen (Visual C++); Daniel K. Allen (Visual C++)
Cc: 'Mike Wescott'; Dan Hogan; navigation@XXX.XXX
Subject: Re: [Nml] Calculators for Navigation
Dan,
My calculator that I  presently use is an HP19BII,  Buisness  Consultant II
which has RPN also.  Do you think that I will be able to use it for what I
will
need for our purposes here on Silicon Sea II ?
Thanks for the help.
T Tom.
Daniel K. Allen (Visual C++) wrote:
> Personally I prefer to spend my time doing lots of programming on my
HP-48GX
> to get sight reduction to the fewest keystrokes!  The HP 48 uses very
little
> power and has great built-in functionality.  It has a strange programming
> language called RPL (Reverse Polish Lisp) but it is quite powerful.  Sadly
> HP is doing very little with calculators any more.
>
> My best nav programs are written in the C programming language and run on
my
> laptops, although I am about to port them to a small HP620LX Windows CE
> machine... which is what HP is putting its efforts to now.  At least these
> machines can be programmed in C -- a big step forward -- but they do not
> support much programming on the machine: you need to write the programs on
a
> desktop machine running Windows 98 or NT.
>
> I've begun experimenting with some nav software written as an Excel
> spreadsheet, and it actually works quite well.  These Handheld PCs that
run
> Windows CE (like the HP620LX and their newer Jornada) have a Pocket Excel
in
> ROM and one CAN program on the handheld machine in Excel simply by writing
> formulas.  (No macros or VBA yet though.)
>
> One of the great advantages of using Excel for numerical calculations is
> that you can see as much of your intermediate results as you want along
the
> way.  You can change just one variable and see how it affects the answer,
> etc.  Writing nav software using Excel is actually pretty promising!
>
> Dan
> danallen@XXX.XXX
>
> -----Original Message-----
> From: Mike Wescott [mailto:mike.wescott@XXX.XXX]
> Sent: Friday, March 12, 1999 6:18 AM
> To: Titanium Tom
> Subject: Re: [Nml] Silicon Sea II: Show of Hands
>
> > What type of calculator is the best for working the calculations, should
> it be
> > programable?
>
> Personally, I prefer minimal computer help for doing the Silicon Sea
> problems
> (and maximal help on the open sea). I use a simple calculator and plotting
> sheets. If I weren't too lazy to use an Ageton method (or one of it's
> relatives,
> I would do without the calculator.
>
> --
>         -Mike Wescott
>          mike.wescott@XXX.XXX
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