# NavList:

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

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Re: stange results from AM and PM sun shots
From: Stan K
Date: 2012 Sep 28, 13:33 -0400
FWIW, the Power Squadrons rule for a 2-body fix knocks off 15º from each end of Frank's rule:  45º to 135º.

-----Original Message-----
From: Frank Reed <FrankReed@HistoricalAtlas.com>
To: NavList <NavList@fer3.com>
Sent: Thu, Sep 27, 2012 2:44 pm
Subject: [NavList] Re: stange results from AM and PM sun shots

Alan, you wrote:
"I get Zn's 269D and 91D in one case, 268D & 92D in another"
That is indeed stange! ...Sorry. Couldn't resist. :)
But I think you're looking at this the wrong way. Do those azimuths make sense? Do they describe what you observed?? You SAW the Sun in the sky. Was it within a degree or two of due east for your morning sights and similarly close to due west when you took your afternoon sights? This time of year, just after the equinox in mid-northern latitudes, that's where the Sun would be just as it's rising and setting. So my guess is that somehow you calculated your azimuths for zero altitude. When you're taking sights, it's always a good idea to record the approximate azimuth of the object. You can even measure it with a compass as long as you remember to correct for the variation. By recording the observed azimuth (which would be accurate only to a couple of degrees in most cases), you have an immediate "sanity check" on your calculated azimuths. In addition, this is the best way to make sure you have a good "spread" in azimuths for a fix. The time-based rule that Brad gave can be useful, but it's not general. All you need to do is make sure you're getting at least 30 degrees separation in azimuth and less than 150 degrees (for a two-body fix or a single body running fix). You observe this visually when you take the sights.
If that doesn't help, I suggest you post your raw sight data.
-FER

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