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    Re: Planetarium Software
    From: Michael Dorl
    Date: 2005 Apr 11, 11:35 -0500

    At 10:53 AM 4/11/05 -0500, you wrote:
    >Could you share your experience, I also want to write
    >something like this.
    >How do you produce the almanac entry?
    All the emphemeris data comes from an adaptation of Stephen Moshier's AA56
    routines, he is (was) at JPL.  AA56 has a crude user interface accepting
    data from the keyboard and producing a few reports.  I took the code,
    removed all the input and output replacing them with a structure with the
    input data and a place for all output and changed it into a dll
    (dynamically linked library).  Thus I now have a library subroutine which
    returns emphemeris data for any object in it's catalog of orbits or
    stars.  The accuracy of the AA56 routines is good enough for me and has the
    advantage of covering a huge time range.  I have used it to produce sky
    charts for Mayan era historical
    events.  I know there are probably better ways to do this using databases
    as pointed out on this list but I prefer the computation method.  I used
    the dll approach because I wanted to get rid of all but a few of entry
    points in the AA routines.
    AA56 is (was) avaialble at
    http://www.moshier.net/  but I can't seem to get
    there now.
    I started my professional life as a computer programmer on scientific main
    frame computers, went on the systems such as DEC Vax VMS and Unix systems
    and ended up spending 15 years or so leading the Network Engineering group
    at the Univ of Wisconsin.  When I retired, I had time to try doing some
    windows programming.  I struggled quite a bit with this getting lost in the
    depths of Microsoft's MFC (Foundation classes) until someone gave me a copy
    of Charles Petzold's 'Programming Windows'.  Petzold advises staying away
    from MFC and with his examples, I was able to do quite a bit although it
    was a painful experience.  You can be judge of how well I succeeded by
    trying my program.
    What more do you want to know?
    >Did you download the almanac/ephemerides data (from a US gov website?)
    >or you compute them?
    >On Mon, 11 Apr 2005, Michael Dorl wrote:
    > > If anyone is interested, I have written a Windows app to do sight
    > > reduction, produce an almanac entry for a given object, and draw a sky
    > > chart complete with constellation outlines.

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