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    Re: Jupiter Lunar DSLR Camera Trial
    From: Antoine Couëtte
    Date: 2010 Nov 11, 01:49 -0800

    Dear Frank,

    Thank you very much for your reply. I now understand how the "Approximate Longitude Error" is computed. And now knowing this " x 30 " magnifying coefficient will maybe help me to unravel the "misteries" about the way you account for planetary semi-diameters. :-)

    Your reply shows that both of us have exactly the same understanding of Lunars. And I find a number of your insights - such as taking a look at the relative position of the Moon's horns and the "other body" - very clever and of great pedagogical value indeed. Very true : your current position of ACTUALLY TEACHING LUNARS gives you an immense advantage here, which I do not have, at least for Lunars.

    I would also thank you for your continual and kind habit of listening to comments and suggestions. Some of them have led to improvements in the display of your On-Line Computer results such as establishing a clear distinction between "Oblateness of the Earth" and "Refractional Flattening", or the more recent possibility to use decimal values for both time and heights, a very nice improvement, at least for me. Regarding the (un)fitness of any computed Lunar for a meaningful UT determination, you have already considered as a "good point" to "add a litte warning of some kind". Implementing such a warning would be great to a number of users and would constitute an "added value" here. I am especially thinking of interested Historians - there must be some - who may not have your sharp and deep understanding of all the relative motions involved. May I also add that the general word "Approximate" necessarily implies - at least in my sense - that we are to remain in the same "order of magnitude", which definitely was not the case here, even if the studied case has a quite exceptional nature.

    Yes, Greg's interest and intention was not about "shooting a conventional Lunar", but about checking the quality of electronic pictures as to their possible fitness to measure Lunar angles. This could rapidly become quite convincing after some improvements which appear within reach. Congratulations to such Pioneers !

    I am sorry to have inadvertently waived the red flag here and that you (over-)reacted to this mention of "TT-UT" value. Certainly at the exact place where I quoted it, it has absolutely no relevance whatsoever. You picked it up right away and I should have removed it from this post. My apologies then. On the other hand, I keep mentionning the exact "TT-UT" value I'am using whenever I publish data about my computed results. This remains the ONLY WAY - and by the way, do you see any other one ? - to help other "number crunchers" (I now know of at least 3 different ones now just on NavList Forum) to meaningfully check their own results against mine.

    One last item : have you tried your On-Line Computer to compute the (very rare indeed) limit cases of Lunar occultations, and if so, what results do you get ?

    Thank you again, Frank, and

    Best Regards


    Antoine M. Couëtte
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