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    Re: Puzzling Sun sights yesterday
    From: Hewitt Schlereth
    Date: 2015 Aug 31, 08:17 -0700
    The app having a hissy fit? :-)

    Hewitt



    On Aug 30, 2015, at 4:37 PM, Frank Reed <NoReply_FrankReed@fer3.com> wrote:

    Just before local noon yesterday I started shooting Sun altitudes near Beavertail Lighthouse with an Astra IIIB sextant fitted with a 7x scope. I used my smartphone app to compare against so that I could record just the intercepts from my known location (identical to sight errors) for each sight. I shot continuously for about half an hour. Index correction and height of eye were pre-entered. Here are the intercepts:

    -0.4
     0.0
    -0.1
     0.1
     0.0
     0.4
     0.4
    -0.6
     0.1
     0.0
     0.3
     0.2
     0.2
    -0.1
     0.2
     0.0
     0.2
    -0.2
    23
    24
    24

    You can see that I've got 18 sights in row with a nice average near zero and a standard deviation of about a quarter of a minute of arc. Very nice! Then... uh... what the heck?? I jump from an intercept of -0.2' to 23'!! Did I read the sextant wrong? Am I going blind? After the third anomalous sight, I was interrupted by some passers by who wanted to learn about my "strange camera". We had a nice chat about sextants and celestial navigation, and then I showed them the wonders of the MarineTraffic smartphone app by identifying a large ship out on the horizon. They were entertained by both, of course. And then I had to head home and get some work done. Later in the evening. I sat down to contemplate that extraordinary jump in intercepts. So put yourself in my shoes: what would you look at if you saw such a bizarre change in your observations and analysis? What could cause such a huge shift? I did discover the cause later, but I would be curious to hear how others would go about "debugging" this one.

    Frank Reed
    ReedNavigation.com
    Conanicut Island USA

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