Starship Asterisk*

alter-ego wrote: ↑Wed Sep 19, 2018 4:49 am

geckzilla wrote: ↑Tue Sep 18, 2018 2:38 pm

alter-ego wrote: ↑Sun Sep 16, 2018 5:06 pm

Yes, but it would be a simulation needing additional image data to be accurate. I can see a telescopic image from Earth taken at an animated image frame time, and then overlaid on the modeled 2D mosaic. LRO imagery alone won't provide enough information to accurately render an eclipse.

I disagree. Accurate coordinates for each object (Sun, Earth, Moon) and a physics-based renderer would not be any less "accurate" than what is already rendered.

I'm not sure if our lines are getting crossed.
No question the LRO mosaics are presented as accurate as they can be. What isn't rendered in the video is the total eclipse. Physics and ephemerides aren't the limiting factors to simulate a total eclipse (I treat "simulate" and "reproduce" the same). I'll say that present prediction / analysis capabilities could reproduce good partial eclipse simulations, but not for total eclipses. To generate accurate color reproduction for total eclipse requires data we don't know well enough (yet). We know that total eclipse color and brightness strongly depends on the integrated atmospheric conditions around the Earth's perimeter. They include clouds, aerosols and moisture. To my knowledge, these parameters cannot be modeled well enough to accurately predict / simulate color and brightness distribution on the fully eclipsed moon. This reasoning is behind my comment that augmenting the LRO mosaic with a full-disk color image of the moon (colors digitized with selenographic coordinates) may yield an accurate reproduction.

With that said, the LRO WAC can capture one good color 60-km swath across the eclipsed surface during it's 2-hr orbit. Maybe that data could "nudge" a predicted color/brightness distribution closer to reality, but I doubt it would be that good.

geckzilla wrote: ↑Tue Sep 18, 2018 2:38 pm

alter-ego wrote: ↑Sun Sep 16, 2018 5:06 pm

geckzilla wrote: ↑Sun Sep 16, 2018 6:51 am ...
Anyway, it's totally possible to put the eclipse into the simulation. One need only include a properly placed Earth...

Yes, but it would be a simulation needing additional image data to be accurate. I can see a telescopic image from Earth taken at an animated image frame time, and then overlaid on the modeled 2D mosaic. LRO imagery alone won't provide enough information to accurately render an eclipse.

I disagree. Accurate coordinates for each object (Sun, Earth, Moon) and a physics-based renderer would not be any less "accurate" than what is already rendered.

alter-ego wrote: ↑Sun Sep 16, 2018 5:06 pm

geckzilla wrote: ↑Sun Sep 16, 2018 6:51 am ...
Anyway, it's totally possible to put the eclipse into the simulation. One need only include a properly placed Earth...

Yes, but it would be a simulation needing additional image data to be accurate. I can see a telescopic image from Earth taken at an animated image frame time, and then overlaid on the modeled 2D mosaic. LRO imagery alone won't provide enough information to accurately render an eclipse.

geckzilla wrote: ↑Sun Sep 16, 2018 6:51 am ...
Anyway, it's totally possible to put the eclipse into the simulation. One need only include a properly placed Earth...

geckzilla wrote: ↑Sun Sep 16, 2018 6:51 am

alter-ego wrote: ↑Sun Sep 16, 2018 5:10 am
You can see that over a full hemisphere, it's not possible for the LRO to capture a lunar eclipse. Given the mosaics are likely many years old, you could say the images are "faults". A lot of calculations and morphing went into those images, but rest assured, though, the representations are very accurate. However,it would have been better to add a sentence in the description stating the images are not snapshots but instead are mosaics built from LRO WAC images taken over the years.

I would go a step further and say that this is not only comprised of many thousands of images to create a mosaic, but that mosaic is applied as a fully 3D model combined with elevation data to render it as realistically as possible. Fun fact: it's hard to create the flat color mosaic at the poles because the Sun never illuminates the terrain from directly above, so shadows are always present

• Feast your eyes on comet 67P's surface, with depth cues added.

alter-ego wrote: ↑Sun Sep 16, 2018 5:10 am

Pat42 wrote: ↑Thu Sep 13, 2018 2:12 pm ...
Btw, there is a fault on the video on July 27th, around 20 UTC. The lunar eclipse is missing !

At first glance that seems to be true. It is not evident from the description that LRO did not take those pictures as real-time snapshots. In fact, it's likely there is no image in that video that was acquired in 2018. Probably all the lunation animations (2011 to present) were derived from the Wide Angle Camera (WAC) near-side mosaic made in 2011 from data (including South-up versions ) The WAC acquires a 60km-wide swath of images (at 50km altitude that's about a 114° field of view!). At that resolution about 600,000 images are required to cover a single hemisphere!

You can see that over a full hemisphere, it's not possible for the LRO to capture a lunar eclipse. Given the mosaics are likely many years old, you could say the images are "faults". A lot of calculations and morphing went into those images, but rest assured, though, the representations are very accurate. However,it would have been better to add a sentence in the description stating the images are not snapshots but instead are mosaics built from LRO WAC images taken over the years.

Pat42 wrote: ↑Thu Sep 13, 2018 2:12 pm ...
Btw, there is a fault on the video on July 27th, around 20 UTC. The lunar eclipse is missing !

BDanielMayfield wrote: ↑Wed Sep 12, 2018 5:51 pm I note that the frame rate of this video is one frame per real time hour. Is it possible to slow down the display rate of YouTube videos? The names of features on the moon and the stats flash by too fast to read.

Bruce

BDanielMayfield wrote: ↑Wed Sep 12, 2018 5:51 pm I note that the frame rate of this video is one frame per real time hour. Is it possible to slow down the display rate of YouTube videos? The names of features on the moon and the stats flash by too fast to read.

Bruce

first98@sonic.net wrote: ↑Wed Sep 12, 2018 8:20 pm No credit to the performers of the Strauss waltz? Shame!

first98@sonic.net wrote: ↑Wed Sep 12, 2018 8:20 pm
No credit to the performers of the Strauss waltz? Shame!

Chris Peterson wrote: ↑Wed Sep 12, 2018 4:48 pm

edgardine wrote: ↑Wed Sep 12, 2018 3:12 pm Earthshine is missing, isn't it ?

Our displays are incapable of simultaneously displaying Earthshine and the illuminated part of the Moon. There's far too much dynamic range. It is possible, of course, to distort the brightness curve in such a way that both are shown, but presumably they chose to simply use a linear scaling, meaning no visible Earthshine (even if their model includes this source of illumination).

BDanielMayfield wrote: ↑Wed Sep 12, 2018 5:51 pm I note that the frame rate of this video is one frame per real time hour. Is it possible to slow down the display rate of YouTube videos? The names of features on the moon and the stats flash by too fast to read.

edgardine wrote: ↑Wed Sep 12, 2018 3:12 pm Earthshine is missing, isn't it ?

ihowarth wrote: ↑Wed Sep 12, 2018 8:50 am Absolutely brilliant animation -- so much information packed into such an elegant presentation.

Not really "N-hemi-centric", beyond the universal convention that N is "up", but a version without the (distracting, barely legible) labels would be nice.

APOD wrote: ↑What is less apparent night-to-night is that the Moon's apparent size changes slightly, and that a slight wobble called a libration occurs as the Moon progresses along its elliptical orbit.

As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible.