Exposing PseudoAstronomy

October 20, 2008

The Apollo Moon Hoax: “No Stars” Claim and an Explanation of Dynamic Range


All posts in this series:

Continuing my sporadic series on claims made by people who believe that the US never landed humans on the moon, I am going to address one of the simplest and yet most prolific claims:  There are no stars in the pictures of the moon.  After all, the sky is black and without an atmosphere we should be able to see stars … right?  WRONG

I am going to address this in three ways, first by proposing questions which demonstrate the lunacy (pun intended) of this claim when you actually think about it.  Second, I will address the reason why we don’t see stars in a qualitative way, and third I will explain dynamic range and why stars aren’t visible in a quantitative way.

Method 1 – Why This Doesn’t Make Sense

The claim effectively goes:  On the moon without an atmosphere in the way, the sky should be filled with stars.  Since there aren’t stars, it must be fake.  In fact, it must be a really bad fake because NASA knew that they wouldn’t be able to figure out where every star goes on their black backdrops for their sets because other people would realize they are in the wrong place, so they just eliminated the stars all together and made the backdrops completely black.

This shows one of the major problems with conspiracy theories of this scale – you have to grant the conspirators a huge amount of power, intelligence, and influence, yet they have to be so unbelievably dumb as to make simple mistakes that the conspiracy theorists can then point out.

When I do my planetarium show on the Apollo Moon Hoax (“Why We Did NOT Not Land on the Moon”), I have the operator bring up the star projector along with a 360° lunar panorama to “simulate” what the conspiracy theorists say it should be like if we’re on the moon.  And it’s a good simulation.  Why?  Because the stars should be in the same place as they are on Earth!  Even though the moon is 384,400 km from Earth, that’s pretty much nothing in relation to where we would see stars from the Apollo cameras.  Only if the astronauts were to do very precise astrometry with very long-focal length lenses (as in telescopes) would they be able to discern any deviation from where the stars would appear from Earth, and even then, it would only be for the very closest stars to our solar system.

So, the fact that we have great planetarium star projectors that simulate the positions of thousands of stars means that NASA should have easily been able to figure out where to put the stars.  And not just that, but if NASA couldn’t figure out where to put the stars – when they had 1 out of every 360 Americans working on the Apollo program in some manner – how would someone else be able to figure out that they were in the wrong place when the exact orientation and location of every single Apollo photograph is simply not available to them?

It simply doesn’t make sense for NASA to have purposely left the stars out.

Method 2 – A Qualitative Explanation of Dynamic Range

Dynamic range (discussed with numbers below in Method 3) is the ability to observe/record/detect a range of values.  For example, if you look at an oven thermometer, it probably has numbers for 100° to maybe 500°.  That’s the dynamic range of it, it can’t record anything below 100° nor about 500°.  Same thing with a car’s speedometer – its dynamic range is probably 0 mph to around 150 mph.  Any speed above 150 and it’s useless.

With cameras, it’s a little more complicated because you can control the “window” of dynamic range with things like shutter speed and aperture.  So let’s go back to the thermometer example – the one above has a range of 400°.  Let’s say I re-calibrated it such that it can now record between -100° and +300°.  Its dynamic range is still the same, but I’ve changed what temperatures it’s sensitive to in the same way changing the shutter speed of a camera will change what light levels can be captured before they’re too dim to be recorded or too bright to be completely washed out.

This is what happened with the stars:  The dynamic range of the camera film was too small to both properly expose the lunar surface and to record stars.  And since, for the most part, the astronauts went to the moon to explore the lunar surface and not do stellar astronomy, they didn’t take pictures of the stars …

… except they actually did (example photo on the right).  Conspiracy theorists never actually bring this up because it’s one of those incontrovertible pieces of evidence that we actually did go to the moon.  Ultraviolet light is blocked by our atmosphere and so it doesn’t reach the ground (for the most part), which is a good thing for life such as us.  To do UV astronomy, you have to go above Earth’s atmosphere, and so the Apollo 16 astronauts actually brought UV cameras to the moon.  They took photographs that were made available, and they were the first of their kind showing features in the far-UV spectrum.  Many years later, when space-based UV telescopes became operational, they confirmed that the Apollo 16 photographs were real because they showed the same things.

Method 3 – A Quantitative Explanation of Dynamic Range

This is a discussion of dynamic range with more numbers.  For ease of argument, let’s say that the dynamic range of the camera film used by Apollo is between 1 and 100.  If only 1 piece of light or less hits the film, the film records it as black.  If 100 pieces or more hit the film, it’s recorded as white.

Now let’s say that the moon reflects between 6000 and 20,000 pieces of light per second, while any one reasonably bright-looking star hits the moon with more like 1 piece of light per second.  (This is actually the approximate scaling between the two.)  This is not because of any atmospheric effects (Earth’s atmosphere transmits over 90% of visible light through it, and it wouldn’t selectively screen out star light from moon light, anyway), but simply because the stars are much fainter because they’re much farther away.

As you can see right away, we have a problem:  Our film can only record between 1 and 100 counts, but the moon reflects over 100 times that amount of light per second.  That’s why we have a variable shutter speed.  We can expose the film for less than 1 second.  In this case, if we expose the film for 1/250th of a second, then the film should only pick up between (6000/250 = ) 24 and (20,000/250 = ) 80 pieces of light in that picture.  Since 24 and 80 are both between 1 and 100, then we have properly exposed the moon, getting its brightness within the dynamic range of the camera.

Now let’s look at the stars.  In that 1/250th second photograph, there’s only a 1 in 250 chance that a piece of light will enter the camera and be recorded by the film.  It’s very unlikely.  And so, to the film, that star wouldn’t even be there – it wouldn’t be detected – because it’s below the dynamic range of the film.

Now let’s say you actually did want to photograph the stars.  With 1 piece of light per second, you would probably want to take a picture for around 50 seconds (to get it in the middle of your dynamic range).  But, if you take a picture for 50 seconds, the amount of reflected light off the moon would be over 300,000 counts, and this is way above our dynamic range limit of 100 counts.  So while that star may be properly exposed in 50 seconds, the moon itself would be over-exposed and appear all white.

That is why the dynamic range of the film is not good enough to see both stars and the moon’s surface in the same length of exposure


To summarize, the basic reason there are no stars in the Apollo photographs of the lunar surface and sky is because the cameras were set to expose the lunar surface properly, and those exposures are too short to record stars.

In fact, you can easily do this experiment yourself:  On a night when there’s a fairly full moon out, or even a half-full moon out, go outside and try to photograph it.  If you use an aperture somewhere around 4.5 to 6.3, you will likely need a shutter speed between 1/200 and 1/100 of a second to properly expose the moon.  Now look at your photos.  Do you see any stars?  The answer will be “no.”

Now try to photograph the stars.  You will likely need to expose for at least several seconds in order to see any stars in your picture.  Now go back to the moon and use the same exposure settings, aperture and shutter speed.  You may get stars in the field this time, but the moon will be a pure white ball, over-exposed.

This simple experiment, along with all the arguments above, should clearly show why the claim that there are no stars in the Apollo lunar photographs does not mean that the lunar landings were faked.

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