# NavList:

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

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Re: learning sight reduction
From: Bill B
Date: 2006 May 3, 21:41 -0500

Alex wrote:

> But still I think the word "challenge"  does not necessary imply
> a duel. We (mathematicians) say "a challenging problem", for example,
> about a problem which attracts us.

Adjective vs. verb ;-)  "I challenge you to..." vs "It is a challenge
problem."

In reality I do use a calculator quite often even when practicing 229.  I
use it at least for v, d, time-to-arc, and final d correction to tabular
data.  Sometimes for interpolation of Z.

With the TI-XA30 (which I consider to be more intuitive for me than the
Casio, especially for one-variable statistics) I can generally determine Hc
and Zn in 3 to 3 1/2 minutes once time, AP, GHA, SHA, declination, d and v
have been established.

General method for standard formulas/sun.

Decimal time increment in memory 1 (M1)
GHA in memory 2 (M2)
Declination in memory 3 (M3)

M1 * 15 + M2, store M2
M1 * d +/- M3, store M3
M2 +/- AP lon, store M2
Decimal lat, store M1

(Actually I just use the sum, 2nd, memory-number sequence to add or subtract
to the to the registers)  Of course there are 2 extra keystrokes to convert
each set of dd/mm/ss to decimal degrees.

For Hc
sin M1 * sin M3 =, + (cos M1 * cos M2 * cos M3) =
Then 2nd sin (store in M2)

For Z
sin M3 - (sin M1 * sin M2)=, / (cos M1 * cos M2)=
2nd cos
If sin LHA (M2) positive, subtract Z from 360 for Zn
(store in M1)

In practice I run Hc at least twice before storing in M2 (little keys are
easy to mispunch).  If the first two do not agree, I run it a third time.

Same with Z.

Zn is stored in M1, so I have Zn recorded in M1 and Hc recorded in M2.

When finished I can recall M1 and M2 and write it down.

I do like the ability to enter dd/mm.m in the Casio.

Bill

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