Apollo 15 Lunar eclipse images

[onebigmonkey]

While picking over the bone of something else to do with Apollo 15, I came across the photographs and TV  taken during the lunar eclipse.

This intrigued me a little so I did some more searching and came across this:

http://spaceflight.nasa.gov/gallery/images/apollo/apollo15/html/s71-58222.html

Which as it says are images taken by the Nikon camera (referred to in the transcripts) during the eclipse. The blurb there mentions the starfield and even a cursory examination reveals that there are several identical features, and that means that we aren't looking at blemishes but actual objects.

So I set to work in Stellarium to find them with no luck. I then resorted to Astrometry.net's website and submitted versions of the images with and without the moon in the middle, all of which returned a site a long way from where the moon should be, so I assumed they were incorrectly interpolated. I then did a manual overlay or white dots on over the brightest stars and resubmitted it (so you get a pure black and white image with no noise). Same result.

I then overlaid the result in Stellarium and it does seem that Astrometry has it correct (see below):



However, while the starfield seems to be focused on the constellation of Aquarius, the moon itself in the Earth's shadow is over in Capricorn (just below the 'pr' in the gif).

Does anyone have any more information about the images. Are they actually of the eclipse? Or even the moon?! If you follow the path of the moon it does not pass where the photo puts it!

(edited to correct web address)

[ka9q]

Do you know the precise location of the CSM when these pictures were taken? There would undoubtedly be a lot of parallax compared to the view from earth.

[onebigmonkey]

That's kind of what I was thinking, but images of Earth before and after the eclipse (which was also recorded on Magazine 96) show it as a thin sliver, which suggests they weren't that far out of the line of sight between sun and moon. The view of the moon in the Hasselblad images is broadly that which we would see from Earth.

The actual event was photographed at 20:34 on August 6th 1971 and was included in a Q&A press conference. The PAO transcript would put it at around 105000 - 110000 nautical miles out from Earth.

Unless I'm missing a trick, Stellarium doesn't allow you to choose a random point in space from which to view things. Certainly there are many images of Earth taken from cislunar space where the visible crescent does not match the view from the moon because of the difference in perspective, but it isn't massive!

[ka9q]

That's kind of what I was thinking, but images of Earth before and after the eclipse (which was also recorded on Magazine 96) show it as a thin sliver, which suggests they weren't that far out of the line of sight between sun and moon. The view of the moon in the Hasselblad images is broadly that which we would see from Earth.

I wouldn't bet on that without checking. I can't remember, doesn't Stellarium or Celestia let you set altitude?

[onebigmonkey]

Stellarium does allow an altitude of up to 99999m - which is just a few short of the 185000000 or so it needs

[ka9q]

Oh well. But since the moon does appear in those photographs, I strongly suspect you are seeing the results of parallax.

Or maybe the photos were faked... 

[onebigmonkey]

Here's an enhanced crop from AS15-96-13111



Which shows there is more of the far side in view than I thought. Might have to see if that kind of detail is resolvable from the TV broadcast!

[ka9q]

I'm not sure what I'm seeing. If the moon is in partial eclipse here, then any reddish area must be on the earth-facing side. So must the sunlit area outside the umbra. If any part of the far side is in view of the camera, it must be completely dark.

But the shape of the umbra doesn't look right, unless we're seeing it from the side?

[onebigmonkey]

I'm not sure what I'm seeing. If the moon is in partial eclipse here, then any reddish area must be on the earth-facing side. So must the sunlit area outside the umbra. If any part of the far side is in view of the camera, it must be completely dark.

But the shape of the umbra doesn't look right, unless we're seeing it from the side?

You're right- it's been kind of doing my head in! The moon was full at the time of the eclipse, so any dark side will have been in shadow. However if you compare what is visible in that image with what is visible from Earth you can see the slight difference in what's on view - the red line is roughly the boundary of the umbra:



So it looks to me as though the CSM is slightly to one side of the normal line of sight, hiding a small portion of the moon from them - or is it just that it's nearer so is seeing less of it at the margins?

I've been trying to get my brain to work out the angles here. A straight line between the star directly behind the moon that is obscured by it (ζ1 Aqr - 55 Aqr - HIP 110960 A) continuing through the moon should intersect a line between the Earth and moon and show where the CSM was when the photo was taken - does that make sense?

~wibble~

My head may explode soon...

[ka9q]

The full moon doesn't always look exactly the same from earth. Remember libration. It's actually pretty substantial, though subtle to the eye. The moon's orbit is both elliptical and inclined to the earth's equator.

[smartcooky]

That's kind of what I was thinking, but images of Earth before and after the eclipse (which was also recorded on Magazine 96) show it as a thin sliver, which suggests they weren't that far out of the line of sight between sun and moon. The view of the moon in the Hasselblad images is broadly that which we would see from Earth.

The actual event was photographed at 20:34 on August 6th 1971 and was included in a Q&A press conference. The PAO transcript would put it at around 105000 - 110000 nautical miles out from Earth.

Unless I'm missing a trick, Stellarium doesn't allow you to choose a random point in space from which to view things. Certainly there are many images of Earth taken from cislunar space where the visible crescent does not match the view from the moon because of the difference in perspective, but it isn't massive!

Apollo follows a curved trajectory, so surely, they could still be close to in line, but their viewing angle could be a long way different if they were closer to the moon.

[onebigmonkey]

And they're heading away from where something used to be to where something eventually will be!

We know when a photograph was taken, we know roughly where it was taken, and we know what it was pointing at, which is great, but I want to know for certain that the difference in viewing location explains exactly what we're seeing in the image.

Diagrams people, I need diagrams!

And whisky for my aching brain.

[onebigmonkey]

...and I should have realised that the AFJ would have such a thing:



I've now adapted that diagram and used it on my page covering Apollo 15's dim light and stellar photography:

http://onebigmonkey.comoj.com/obm/page5.html