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I've been searching Horizons settings to find lunar librations but can't find. How can I get the libration data?

So I have tested this Horizons Web Application and selected Moon as the target. Whether I select Vector Table or Osculating Orbital elements or Observer Table as Ehpemeris Type there's no lunar libration column in the output data. I'm expecting two parameters like libration_lon, libration_lat or something. I've tested both ecliptic and equatorial reference planes (in Table Settings).Screenshot of Horizons Web Application

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  • $\begingroup$ Where exactly did you look and what exactly did you search? $\endgroup$ Oct 6, 2023 at 14:42
  • $\begingroup$ @planetmaker I edited the question with some details. $\endgroup$ Oct 6, 2023 at 15:11
  • $\begingroup$ Thanks. I also added the actual link to the web app. $\endgroup$ Oct 6, 2023 at 16:05

1 Answer 1

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For Ephemeris Type, choose Observer Table. Under Table Settings, select:

  1. ☑ Observer sub-lon & sub-lat

They don't use the word "libration" because it also applies to other bodies e.g. Mars. Then the output has:

 'ObsSub-LON ObsSub-LAT' =
   Apparent planetodetic longitude and latitude of the center of the target
disc seen by the OBSERVER at print-time. [...]

Note that at 1 lunar distance, the observer's geographic location can change the results by as much as 1° due to parallax.

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