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Posted by M C Butcher at 17:17 on 2013 Oct 03
I am attempting to understand what the values for lunar libration contained in the BAA Handbook actually mean with respect to the lunar disc. My questions are:a. I believe that on the Lunar disc North is up, South is down, East is right and West is left. Is this correct?b. The position angle given on page 19 of the BAA Handbook is from North (000 degrees) round to North (360 degrees). Is the measurement made clockwise or anti-clockwise? The note at the bottom of Page 19 is ambiguous.c. What does the value contained on page 19 actually measure? Does it, for instance, show where the centre of the Lunar disc has moved TO (ie the extra part of the lunar disc displayed is on the opposite side away from the Libration shown); or does it show the location on the Lunar disc of the new centre (ie it is indicating the lunar limb that displays greater exposure?d. On checking the Lunar Section Circular for May and June/July 2013 with the table on page 19 it would seem that the libration is measured anti-clockwise from North, however, the values graphically portrayed bear only a passing resemblance to those given in the table. Possibly I am expecting too much from the graphical presentation in the Lunar Section Circular.Can anyone help please?Martin Butcher
Posted by Sheridan Williams at 17:59 on 2013 Oct 09
I have a comprehensive answer to this question and if Martin and others would like a copy, please email me at: britastro@clock-tower.com.Sheridan WilliamsDirector of the Computing Section(Responsible for the Handbook)
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