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    Re: Longitude by Lunar Occultation
    From: Paul Hirose
    Date: 2019 Jan 10, 20:24 -0800

    On 2019-01-08 14:45, Robin Stuart wrote:
    > Maybe the software available on the sight can produce a list local 
    circumstances of stars down to magnitude 6.5 but I wasn't interesting in 
    digging around in it. I also thought it was pretty unlikely to compute 
    longitude and GMT given latitude and local mean time,
    
    No, the IOTA site doesn't do any of those things. But it does provide
    occultation predictions for sites in its database. These can be used as
    test problems. For instance, see the January 18 occultation of zeta Tauri.
    
    http://www.lunar-occultations.com/iota/bstar/0118zc847.htm
    
    The first site on the list is Benguela, where disappearance occurs at 18
    14 36 UT. Further down the page we see that re-appearance is at 19 19
    20. Still further down we see the coordinates of site Benguela: S 12
    36.5 E 013 24.2. (On the web page the format is east longitude first,
    latitude second.)
    
    If your software is accurate it should closely match that prediction. My
    Lunar program has zeta Tauri .02′ outside the limb at the disappearance
    time given at the IOTA site, .01′ inside the limb at the re-appearance
    time. If I apply the conventional offset for center of figure, the
    re-appearance improves a tiny bit to .00′, but there's no change at
    disappearance.
    

       
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