Apollo 11

Landing: 102.75 GET EVA

Start: 109.00 GET, 14.0 deg.

Finis: 111.75 GET, 15.4 deg.

According to NASAs website the sun angles during apollo 11 mission is the ones stated above. At 15 deg an object of 1 meter would cast a shadow length of 3,7 meters. Yet, the images from apollo 11 mission show objects cast a shadow of roughly 2 meters for every 1 meter in height. To achieve the latter, the sun would have to be at 26,5 deg.

Why this discrepancy?

A fitting apollo 11 image:

enter image description here


The major factor here is foreshortening. Unless a photo is taken exactly perpendicular to the shadow cast by an upright object, the apparent length of the shadow will be shortened by the perspective. In your example case, the photo seems to be taken somewhere around 45-60 degrees off perpendicular; taking the cosine of that tells you the shadows appear at somewhere between 0.5 and 0.7 times their actual length, which gets you near enough to your expected 3.7:1 stretch factor.

Here's a top-view diagram of how that works.

enter image description here

A smaller factor is the unevenness of the lunar surface. It's notoriously difficult to estimate the elevation changes from the Apollo photos. Shadows falling on an uphill slope will be shorter than expected.

You also reference a near-perpendicular-shadow picture:

enter image description here

I am able to nearly reproduce the geometry of the image in a 3D tool using a 53.5º field of view and a 15.3º sun angle. It's not a perfect match, but I don't know the exact dimensions of the box or geometry of the terrain:

enter image description here

(Clearly, The Conspiracy has reached Unity Technologies.)

Additionally, the debunking site Clavius.org has some nice sets of photos showing how the same shadow can look very different from different directions. You may enjoy some of the other photo analysis pages on that site.

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  • $\begingroup$ Thank you for an thorugh explanation. I'm not totally convinced by the foreshortening explanation and it's hard to find perpendicular shadows in images from apollo 11. After sifting through NASAs apollo 11 images this one is quite interesting and indeed perpendicular. It appears to have the same ratio as in the other images og 2 meter shadow per 1 meter object height. How is this possible with the shadow on the box infront of the astronaut being completely perpendicular? hq.nasa.gov/office/pao/History/alsj/a11/AS11-40-5946.jpg $\endgroup$ – Otis Aug 11 '17 at 7:03
  • $\begingroup$ That's nowhere near a 2:1 ratio, though -- for the shadow coming off the box, I measure 271 px shadow length and 82 px box edge, for a 3.3:1 ratio. That does require a 26 degree off-angle, which is more that I'd have guessed from the composition of the picture, but it's not impossible. $\endgroup$ – Russell Borogove Aug 11 '17 at 14:25
  • $\begingroup$ I get 3.03:1 ratio when measuring the image in the high res version. There's still a discrepancy not accounted for. 18.26 deg will cast that shadow. Something fishy is going on ;) $\endgroup$ – Otis Aug 11 '17 at 19:03
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    $\begingroup$ @Otis: There's nothing fishy going on. There are a few sad things going on. One of the sad things is the dwindling number of living people who had once walked on the Moon. Only six of the twelve men who walked on the Moon are still alive. An even sad thing is the growing number of people who disrespect those six, the six who died, the twelve who went all the way to the Moon but never landed, and the hundreds of thousands who worked on making than happen. The disrespect is believing the utter nonsense that this never happened. $\endgroup$ – David Hammen Aug 12 '17 at 1:10
  • $\begingroup$ @DavidHammen very well put, thank you for that. Only tangentially related, this clip is queued to start just before the third "conspiracy" skit, but the first skit is also "space" related. youtu.be/5muY64Oyp10?t=276 $\endgroup$ – uhoh Aug 12 '17 at 18:40

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