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Libration of the Moon

[edit]
*** REPLACEMENT IMAGE ***
Although the Moon keeps the same side towards Earth, careful observations will reveal you can actually see 59% of the Moon's surface. These variations are caused by the fact that the Moon rotates at a constant rate, but travels around Earth at a variable rate, being in an elliptical orbit and moving faster when it is closer. This animation shows a set of 50 simulated views of the Moon from the center of the Earth over one draconic month.

This is a striking animated image--created by Tom Reun using NASA/USGS images--that illustrates an effect few people know about (including myself until reading its source article, Libration).

  • I really liked the image, and the idea. Here's an animation I did using a solar sim. It's 1.2 mb in size, and has a tiny hiccup (caused by the very observation above) but it's an illustration of what's good (and bad) about a plainer approach. It currently has no shadow calculation applied, so the moon's phases are not visible. It's slow until it finishes loading, necessitating an optimized version (if folks here find it valuable, I'll get to it :)
See http://en.wikipedia.org/wiki/Image:Libration-noshad2b.gif
Right to high-res version: http://upload.wikimedia.org/wikipedia/en/e/e6/Libration-noshad2b.gif
The Libration of the Moon, roughly Jan 13-Feb 12 2005 -- RyanFreisling @ 04:19, 28 August 2005 (UTC)[reply]

CapeCodEph 21:14, 28 August 2005 (UTC)[reply]

      • I much prefer the faster version, however they both do a good job of illustrating the article. I would be happy with either, but I'd prefer the faster one. Raven4x4x 00:19, August 29, 2005 (UTC)


  • Greetings from: Tom Ruen 06:38, August 30, 2005 (UTC)
    • I got an email from CapeCodEph. I can remake the animation, cleaned up, if there is a consensus on what we should do. (I wrote my own program, but it's not automated, interactive on each frame capture, so takes a little work...)
    • Questions for consideration:
      • How many total frames? (Currently ~30 I think, ~1/day)
      • How many frames/second? (Unsure current, probably ~10?)
      • How many pixels? (Obviously bigger is slower, but multiple versions could be made from a higher resolution image)
      • Do we want to include the light phase? (Not directly important for the Libration article)
      • Any text/symbols? Crosshairs, time, location, field of view?
      • Also there's different lunar bitmaps available for projection:
      • Incidentally the "skipping" from start to end is "real" since the libration doesn't repeat each month the same way. No easy way to hide it.
    • Well, I don't expect agreement, but if someone wants to be dictator/unifier, I can try whatever is suggested, probably Friday night...
I think you can still get a version that doesn't skip. Like taking pictures at a different interval than exactly a day apart? — Omegatron 13:27, August 30, 2005 (UTC)
    • I'm sure it can't match exact because there's different periods involved:
      • Node period: 27.2122d (N/S Librarion)
      • Perigee period: 27.5546d (E/W Libration)
      • New moon period: 29.5306d (Phase)
    • I used the phase period. If I drop the phase rendering and use the node or perigee period, it should be much more smooth, although still some jump in one or the other. But agreed MUCH smaller. Tom Ruen 19:07, August 30, 2005 (UTC)
  • Tomruen, why did you revert to the old version with the text on it? I thought we agreed the new version was better? Raven4x4x 05:10, September 3, 2005 (UTC)
      • Hi Raven4x4x - Sorry I must have pressed something without intending it. Tom Ruen 20:32, September 4, 2005 (UTC)
      • So does that mean it should be reverted back? I don't want to do anything to your image without your permission. Raven4x4x 07:32, September 5, 2005 (UTC)
  • Support: it's educational and interesting. Jdhowens90 10:33, 3 September 2005 (UTC)[reply]
  • Support the fast version. — BRIAN0918 • 2005-09-4 17:29
  • 'Question: What does "Center of the Earth" mean? When I hear that phrase I think of the Earth's core, which doesn't seem right. Does it just mean that we are following the moon as it rotates around the Earth? Can the caption be clarified or at least an explanation be put on the image description page? --Fastfission 17:49, 4 September 2005 (UTC)[reply]
    I think it actually means the core of the Earth. Obviously in this simulation the Earth is transparent. — Omegatron 18:53, September 4, 2005 (UTC)
    • YES, My program has 3 view mode: Center of earth (Geocetric), surface of the earth (topocentric), and hovering over the earth. The label is generic, but still valuable to know all the motion is due to the moon's motion and not the earth spinning. Tom Ruen 20:32, September 4, 2005 (UTC)

Promoted Image:Lunar_libration_with_phase2.gif CapeCodEph 03:00, 10 September 2005 (UTC)[reply]

Candidate(s) for replacement image

[edit]
    • [Image:Lunar-libration.gif]
    • No phase, 50 frame.
    • Since perigee distance varies the most between periods, I started the sequence on apogee.
    • I used the Draconic period (27.21222 days)
  • Comments?
  • Tom Ruen 05:55, September 5, 2005 (UTC)
    Is it just me or is the crosshair wiggling? I actually liked the wildly changing date and time, but not the other window stuff. — Omegatron 06:06, September 5, 2005 (UTC)
  • No, I much prefer the other one (the version without text). The wiggly crossair is rather annoying, and because the animation no longer shows the phases of the Moon, it just looks unnatural. I would not support this version. Raven4x4x 07:30, September 5, 2005 (UTC)
  • Okay, here's another option:
    • [Image:Lunar libration with phase.gif]
    • Added phase back, added time, and removed crosshair
    • I made it smaller (~1M) partly because I'm on a slow modem connection at the moment!
    • Note the phase jumps a bit because I'm using the Draconic 27.21 day period of the libration rather than than the phase period (29.53 days), but overall it is pretty smooth.
    • Tom Ruen 16:50, September 5, 2005 (UTC)
  • The second file is an amazing image, and a great improvement! I think the lack of phases and huge size of the first replacement option make it unattractive, though you're right on the money with the second one. Two suggestions: adjust the text so that it doesn't overlap the image at all (you may have to expand the image size a bit), and switch to 24-hour time (including leading zeros and without am/pm) to eliminate the jumpiness of the text. 1 meg is definitely large enough, so if you try to eliminate that phase skip, stretch it out of the current number of frames. You may try a slightly slower version as well, as it doesn't detract much from the effect, and it makes the animation easier to absorb. CapeCodEph 21:34, 5 September 2005 (UTC)[reply]
  • I like that one! Can you space the time and date so that they are always in the same exact place, instead of the line getting shorter and longer? That is my only complaint about this one. — Omegatron 23:34,

September 5, 2005 (UTC)

  • Cool, I like this one. Support this new version. Raven4x4x 23:54, September 5, 2005 (UTC)
  • Another option:
    • [Image:Lunar libration with phase2.gif]
    • One more attempt - a bit smaller (954k), fixed-width font stays aligned, 24 hr time
    • Brightened source bitmap a bit before projecting.
    • Capecodeph, in regards to "eliminate the phase skip", if you mean going to a 29.53 day period, it would cause more motion jumping on the libration orientation.
    • Tom Ruen 00:52, September 7, 2005 (UTC)
  • Well done, Tom! Trust your judgment on the "phase skip" I mentioned, and the new font and speed are a lot nicer. Tomorrow is the end of the 14-day voting period for this Featured Picture, though, so you should update the main photograph with your final version. CapeCodEph 21:58, 7 September 2005 (UTC)[reply]
  • Support this final version. — BRIAN0918 • 2005-09-8 00:20

Final replacement

[edit]

I substituted this image for all the image:moonc.gif images on wiki:

  • Image:Lunar libration with phase2.gif

Tom Ruen 03:27, September 8, 2005 (UTC) Promoted Image:Lunar_libration_with_phase2.gif CapeCodEph 03:00, 10 September 2005 (UTC)[reply]

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