NavList:

Gary LaPook writes:
I have no idea how it could take ten minues to calculate Hc and  Zn on a pocket digital calculator, I just did a sample test and it took me 58 seconds. I use the standard formula for Hc rearranged to the form:

Hc = arcsin (cos LHA x cos dec x cos lat + sin lat x sin dec)

and  Z = arcsin (sec Hc x sin LHA x cos dec) since implementing it this way saves a few keystrokes. Using a TI-30 with only 3 memory locations the key strokes are:

(When entering values in the format of degrees.minutes seconds, change decimal minutes to seconds, 6 seconds per tenth of a minute, in your head  before punching in the assumed latitude, declination  and for the  GHA and assumed longitude entries.)

Assumed Lat
2nd DMS-D.D (changes to decimal degree format)
STO 1  (stored A. LAT in 1)
Declination
2nd DMS-D.D
STO 2   (stored DEC in 2)
GHA
2nd DMS-D.D
-
Assumed Longitude
2nd DMS - D.D
= (computed LHA)
STO 3   (LHA stored in 3)
COS
X
RECALL 2  (recalled declination)
COS
X
RECALL 1  (recalled Assumed latitude)
COS
+
RECALL 1 (recalled A. LAT)
SIN
X
RECALL 2  (recalled DEC)
SIN
= 
2nd SIN  (ARCSIN, computed Hc)
STO 1  (stored Hc in 1) (you won't need the  stored A. LAT again)
COS
1/x   (converts COS Hc to SEC Hc)
RECALL 3  (recalled LHA)
SIN
X
RECALL 2  (recalled DEC)
COS
=
2nd SIN  (ARCSIN, computed Z)
RECALL 1  (recalled Hc)
2nd D.D - DMS (changed Hc in decimal degrees to degrees, minues and seconds)

da-da!

done

58 seconds flat..

gl





Anabasis75@aol.com wrote:

gcurte wrote:

>hello every one,
>
>i 'm trying to  get a hendheld calculator to expedite my sight
>reduction work.
>if i use a regular sciencefic calculator it take me like 10 minutes
>per sight. some time i want to trevel light so a calculator will be a
>good help.

 

Jeremy says:  with practice, this will be down to a minute or two.  I can do a full HO 229 star reduction in under 3 minutes using tables.  With a calculator it can be quicker.

>i can see on internet are a lot of programs ,softwhere   and many
>others. the problem with the little palms or pocket pc they depend on
>recargebile battery, that mean if you  are somere isoleted you ca not
>use it for long time. i see  the starpilot as a good alternative for a
>long period of time but reading the instruction on internet

 

Jeremy says:  I would suggest one of the navigational calculators over a palm or pocket PC.  I have some self-programmed software on my 15 year old TI-85 calculator which uses AAA batteries and lasts for a year or more on a single set of cells.  Also, my 32 year old navigation calculator runs for a year or two on 4 AA batteries, even with fairly regular use.  I believe the Starpilot is software in a TI-83 calculator, so I can't see why that wouldn't last for many months as well, and spare set of AAA cells should be easy to carry.

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