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Lunar Libration PA

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Lunar Libration PA

Posted by John ONeill at 11:22 on 2012 Dec 20

Hi,I have noticed an apparent discrepancy between the Lunar Libration P.A.s in the BAA Handbook 2013 (p.19) versus those in Guide 9. The size of the Librations agree.For example: I have set the position in Guide 9 to geocentric and the date to 2013 Jan 2.30 UT.Guide 9 gives:Libration in latitude: 6.53 degreesLibration in longitude: -6.31 degreesTotal libration 9.1 degrees, at limb angle 44BAAH 2013 gives:Size 9.1 deg PA 66 degI have checked the same date in MICA 2.22: Selenographic Coordinates Date Time Earth Sun (UT1) Lat. Long. Lat. Long. h m s ° ° ° ° 2013 Jan 02 07:12:00.0 6.548 -6.318 1.17 298.58 Am I missing something?John

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Re: Lunar Libration PA

Posted by Sheridan Williams at 14:16 on 2013 Feb 06

Just noticed your post. I will check and get back to you.

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Re: Lunar Libration PA

Posted by Richard Miles at 22:51 on 2013 Feb 11

I wonder - Could this difference be related to the tilt of the Earth on its axis projected on the sky.Note that the P.A. quoted is measured through East on the face of the Moon from the north point of the disk and NOT from the North Pole of the Moon.Richard