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Gary LaPook wrote:

I programed a Casio calculator years ago to do celestial computations. I
would occasionly end up with "divide by zero" and other errors. Rather
than write complex code to test for various conditions I simply added
.000001 to some values (I forget which ones) so they would never equal
zero and adding this slight fudge factor didn't make any noticable
difference in the computations.

Guy Schwartz wrote:

> Bill:
> Thank you.
> Your answer is the missing piece to my puzzle
> I now added a test for sine of LHA >0
> 8-).
> Guy
>      Hc and Zn by calculation using casio fx 260 calculator
>     Sin-1Hc = sin(dec) x sin(lat) + cos(dec) x cos(lat) x cos(LHA)
>
>       sin(dec) x sin(lat) =
>      A= 0.207883238 X 0.644790904 0.134041221
>     cos(dec) x cos(lat) x cos(LHA) =
>      B= 0.978153648 X 0.764359006 X 0.965389226 0.72178344
>         Total A + B 0.855824661
>      Declination,  +North -South  North Shift Sin-1(Hc)  58.85095947
>      Latitude,  +North -South  North 0999 Hc 58? 51.1'
>
>     Cos-1 (Zn)= sin(dec) - sin(lat) x sin(Hc) / cos(Hc) x cos(lat)
>       cos(Hc) x cos(lat) =
>      A= 0.517255471 X 0.764359006 0.395368878
>       sin(lat) x sin(Hc) =
>      B= 0.644790904 X 0.855831045 0.551832073
>       sin(dec) - B =
>      C= 0.207883238 - 0.551832073 -0.343948836
>       C / A =
>      D= -0.343948836 / 0.395368878 -0.869944134
>         Shift Cos-1 (Zn) 150.4521481
>         0999 Zn 209? 32.9'
>
> ----- Original Message -----
> From: "Bill" 
> To: 
> Sent: Monday, May 29, 2006 4:00 PM
> Subject: Re: Z or ZN and a couple other fx 260 to excel conversions
>
>
>> Guy wrote
>>
>>> I was working out a problem here are the particluars
>>> DR 40 deg 9 min N
>>> 45 deg W
>>> object Regulus
>>> Dec 11deg 59. 9 min N
>>> LHA 16:25:48
>>> HC 58 Deg 20.4 Min
>>> Using HO 249 the Z is 150 and the ZN is 210 I also checked with the
>>> star
>>> section and the ZN was the same.
>>> When I did the calculations using
>>> Cos rasied to -1 (Zn) = sin (dec) - Sin (lat) x sin (Hc) / cos (Hc)
>>> x cos
>>> (lat)
>>>
>>> The answer came out to 148 deg 11.4 min which is close to the 150 Z
>>> however I
>>> though that formula gave me the Zn?
>>
>>
>> Yes and no, it is situational as the HC can be the same at some point
>> before
>> and some point after noon (using the sun as an example). With the sun
>> LAN
>> (local area noon, sun at its highest point) is also the upper meridian
>> passage. For any body, LHA = 0 for upper meridian passage.  To
>> extract Zn
>> from Z,  determine whether the body is rising (pre meridian passage) or
>> setting (post meridian passage.
>>
>> If rising, Zn = Z.  If setting, Zn = 360 - Z.
>>
>> When in doubt, if the sine of LHA is positive, Zn = 360 - Z.  When the
>> sine
>> of LHA is negative, Zn = Z.
>>
>> My memory device is "plus minus."  When the sign of sine LHA is PLUS,
>> Zn =
>> 360 MINUS Z.
>>
>> Bill
>>
>>
>> --
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>>
>>
>

   

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