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    Re: Learning Lunars
    From: Antoine Couëtte
    Date: 2010 Feb 26, 12:06 -0800

    Well, Jeremy ... I knew about the existence of Lunars since the very early 1970's, but never got interested in them until Nov 2008 when I happened to discover the NavList Forum, while by the same token discovering that some Lunarians were still in existence here and there somewhere on Earth and that their species was not a totally extinct one...

    I had been earlier been programming Celnav on my HP25-C since 1977, then on my HP34-C since 1980, and then on my HP41CV since 1981. HP41's eventually got improved through the years into the then extraordinary HP41CY "top model" with 64 k of quasi ROM which was on the Market by the mid 1980's.

    And some 10 to 15 years later, when the HP41 was really starting going downhill, then TWO WIZARDS and REAL MAGICIANS, Jean-François Garnier from France and HrastProgrammer from Croatia put an HP41Y emulator (exact HP41 system replica) running on the HP48GX (HrastProgammer) and also under MS-DOS on a Computer (Jean-François Garnier) . So I saved then all these 20++ years of software programming. See the full story in http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv016.cgi?read=91719#91719.

    Note : the HP41 Programming language, with its 4 level stack is perfectly well adapted to 3 dimension computations, and it is probably (and by very far I would think) the most concise scientific language ever, ... but it is not an easy one if you want to optimize it "size-wise", or if you want to analyze a (already concisely optimized) software written by somebody else even if you are most familiar with the subject being tackled.

    Through peering here and there on NavList, I immediately recognized that the "Classical" Methods carried some limitations which I really disliked at once . Since I still had @ 1800 bytes left unused, and after hesitating for a full 3 month period - I knew and feared that it would not be an easy task at all with such a tiny remaining allocable programming space - I did take up the challenge and then decided in Feb 2009 to invent a totally new computation method, which I first devised in "theory" and then put in "practice" in my new software.

    By the early summer 2009, everything was fully completed and run 4.0 for conventional Lunars, and just within the allocable remaining space (only 3 bytes left). By that time I remember then calling George Huxtable on the phone from the USA where I had just landed and asking him how I could become a NavList member ... and once registered among you, I then had the pleasure and very nice surprise of discovering an extremely kind word of Warm Welcome from George on our Forum. Thank you again George.

    My Lunar software kept itching me ... I then decided to attempt improving it to also deal with the Lunar Occultations, a "limit case" with Lunar distances equal to zero. These are very much more delicate computations, a subject recently addressed by Frank E. Reed. YES, I DO fully agree with you on this, Frank. I eventually and successfully improved my software into dealing with Occultations too, and at no extra cost in programming space. Still ... 3 bytes left over an initial number of some 64 000.

    Total work here required certainly well above 6,000/7,000 hours over this 30 year time span.

    Since them, and time permitting, I have been playing with a number of examples, including our French Navy Captain Arago recent postings and an even more recent Aldebaran Occultation example taken from Jean Meeus.

    Again I wish to thank some of our most knowledgeable NavList members ( Paul Hirose, and "M. waldendand---com" ) who very kindly and just recently worked out these same examples with their 3 different and independent software, not to forget Frank for his excellent On Line Lunar Computer - which I even used as an Occultation Computer lately - and also George who was the first one to whom I submitted my own solution of a Lunar (Moon and Mars if I can remember correctly, which you published some 4 years ago in a long series of very interesting posts) and for which I had not been able to find any published solution on NavList.


    Thanks to you all ...


    From what I can see .. Lunars are a lot of fun !!! maybe not for (all) spouses, though !!! I can testify !

    And I would really have liked to take pictures of your bewildered friends, Jeremy, when your trained yourself to shoot Lunars.


    .. now, back to my exams preparation.


    Anyway, it was a quite nice (and quite extended and most appreciated) break time for me !!!


    Antoine M. "Kermit" Couëtte
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