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    Re: Tinyac almanac program for Windows
    From: Paul Hirose
    Date: 2010 May 13, 15:42 -0700

    Dave Walden wrote:
    > lat seems to effect geocentric LHA? 
    
    It shouldn't, and I haven't noticed that it does. For example, body =
    Sun, topocenter = Griffith Observatory (the default), time = 2010 May 13
    2200 UT1 (delta T = 67.781 to match the USNO MICA program), coordinate
    reference system = apparent geocentric geodetic (LHA) of date. Tinyac
    says LHA = 32°37'08.8", lat = +18°31'46.4".
    
    Turning to MICA at the same time, GAST = 13 26 12.1065, true geocentric
    RA = 3 22 31.920. GHA = GAST - RA = 10 03 40.1865 (time) = 150 55 02.798
    (arc). Subtract the longitude of the topocenter (118 17 54.0) to obtain
    32 37 08.8. Declination = 18 31 46.45. These are identical to the Tinyac
    values.
    
    Now switch Tinyac to topocentric origin, leaving other settings
    unchanged. LHA = 32°37'12.7", lat = +18°31'43.8". In MICA, get the
    apparent topocentric RA and dec and repeat the steps above. Again, the
    match is perfect. (For this test I used the built-in SOFA ephemeris to
    show that it's impressively accurate in the present epoch for the Sun.
    It's equally good for the Earth. Other bodies are considerably less
    accurate, though.)
    
    By the way, an HTML message is not a reliable way to get my attention.
    (See my sig.) If there were any other replies, I missed them. I wasn't
    watching my Trash folder for filtered-out messages because I figured the
    user base for this program would be somewhere between negligible and
    nil. Besides, I do make it clear there's a filter.
    
    I'll try to pay more attention from now on, but there's a good deal of
    trash to look over each day, and I don't do it very carefully. I've
    never been one to fret about missing a few messages. That casual
    attitude includes my own postings. If one failed to show up (which I
    don't think has happened here yet) I probably wouldn't bother to repost
    or make an inquiry.
    
    -- 
    I filter out messages with attachments or HTML.
    
    
    

       
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