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S&T moon globe quirk

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#1 GlennLeDrew

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Posted 31 December 2012 - 04:37 AM

A friend had this very fine moon globe dropped off by Santa. While examining it I noted a strange discontinuity, more obvious near the poles. It took perhaps 30 seconds to realize what was doing this. The 90 degree sector immediately west of the near side's western limb (longitude 90W to 180?) uses imagery where the sun angle is reversed, it being 'afternoon' vs 'morning' for the other 270 degrees.

Is this universal? (I didn't read any included material.)

#2 swalker

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Posted 31 December 2012 - 12:44 PM

This is due to the data produced by the LRO team. While the lighting is different in small sections, the positions of features are still accurate.

#3 GlennLeDrew

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Posted 31 December 2012 - 06:59 PM

Sean,
Too bad a uniform lighting angle could not have been obtained for the entire Moon. Any reason for this?

I haven't scrutinized sufficiently closely (having only briefly checked it out on Xmas day), but it seems the discontinuity is precisely following the two lines of longitude. Many craters are thus bisected, resulting in a kind of 'schizophrenic' lighting. Could not at least the more prominent craters have been spared this by manually zig-zagging the discontinuity around them?

#4 swalker

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Posted 02 January 2013 - 03:51 PM

You're unfortunately barking up the wrong tree- the LRO team generated the global skin used to make the Moon Globe, and I simply tweaked the contrast, as well as stitching in a few areas in the polar regions where some craters were chopped in half by poor lighting. This was only possible because the poles were released as individual images a few years ago on the LRO website. No such patches were possible when deviating far from the poles due to severe distortion and even less appealing lighting.

The major work we did here at S&T was labeling features, not assembling the global mosaic; none of us here have the time nor computational power to assemble 25,000+ images into whats known as hemispherical "daisies" to make a globe.

#5 faackanders2

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Posted 02 January 2013 - 08:57 PM

Too bad they couldn't reposition the sun at both poles, so they could get even photographic lighting. :foreheadslap: :tonofbricks:






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