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

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Re: Z or ZN and a couple other fx 260 to excel conversions
From: Greg R_
Date: 2006 May 29, 13:57 -0700
Guy:

> 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?

Don't forget that when you reduce a sight by tables (at least for HO 229 and 249, I can't speak for any of the other ones) you're using a whole number for Latitude and LHA for your AP (which usually isn't the same as your DR position).

Doing the reduction by calculator will give you an "exact" answer for whatever you put in for your DR position. I haven't tried it, but I think if you plot both LOPs you'll find that they'll land in the same geographical position (i.e your Zn of 148 deg 11.4 is the azimuth of the intercept from your AP for that sight, which is not necessarily also your DR).

I'd also be glad to check your math with Navigator Light and see what it says (theoretically should be the same results as a calculator), but you didn't include a time for your sight, and it's kinda hard to reduce something without one.. ;-)

> what is the equalvalent function in excel to the Shift Sin-1

Aha - two minds on the same wavelength. I just setup a little Excel spreadsheet the other day to do sight reductions - the function you're looking for is ASIN, but don't forget that Excel works in radians and you need to do that conversion first:

=SIN(A4*PI()/180)

where A4 = cell location for Lat value in this case.

BTW, if you (or anyone else) has an easy way to do trig calculations in Excel based on the DDMM.M format that we use with sextant sights I'd love to hear about it. My current workaround requires entering Degrees and Minutes.Decimals as two separate entries to do the math - a bit unwieldy, but it seems to work.

--
GregR
(doing some celnav practice on this Memorial Day holiday)

----- Original Message -----
Sent: Monday, May 29, 2006 11:56 AM
Subject: Z or ZN and a couple other fx 260 to excel conversions

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?

New question, what is the equalvalent function in excel to the Shift Sin-1
and the Shift Cos-1
Thank you.
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 0.959166009 0.717130586 Total A + B 0.851171807 Declination,  +North -South Shift Sin-1(Hc) Latitude,  +North -South 0999 Hc Cos-1 (Zn)= sin(dec) - sin(lat) x sin(Hc) / cos(Hc) x cos(lat) cos(Hc) x cos(lat) = A= 0.524877545 X 0.764359006 0.401194878 sin(lat) x sin(Hc) = B= 0.644790904 X 0.85117775 0.548831671 sin(dec) - B = C= 0.207883238 - 0.548831671 -0.340948434 C / A = D= -0.340948434 / 0.401194878 -0.849832469 Shift Cos-1 (Zn) 0999 Zn

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