Yeah there is. Stars are relatively dim and can not appear in the same picture with a bright sunlit object. The necessary exposure settings for each are too different.
Yeah, we associate a black sky as being the night time (the conditions when we normaly can see stars). However, the photos from the moon are actualy taken in daylight, the lunar sky looks black because of the absense of an atmosphere. I imagine the stars are actualy visible in these contition on the moon, however the exposure needed to photograph them would wash-out the brightly lit objects in the foreground.
"Feels good to be breaking the laws in America again" - Kenny Powers
We are all in the gutter, but some of us are looking at the stars.
Posted 07 March 2007 - 11:53 PM
Please forgive me for posting what is esentially a repeat of a post I made back in June in another thread. In that thread it was claimed that the lack of stars in the Apollo photographs was proof that the photos and, therefore, the missions, were faked. This was my reply to that accusation:
Why the Apollo photographs don't show any stars in the lunar sky
One of the most common claims of the hoax believers is that you can tell that the Apollo photographs are fake because there are no stars in the sky in any of the photographs. They argue that with no atmosphere stars should be visible on the moon in daylight. The fact that there are no stars proves the photos are fake.
There is an element of truth to this. Stars should be visible to the eye, in daylight on the moon. Photography however does not work in the same way as the human eye.
A basic knowledge of photography will explain why there are no stars in the Apollo photographs, yet despite the fact that just about every basic photography book on the planet will give the explanation, this false accusation is still made over and over again.
Some time ago I decided to back up the simple explanation with some photographs to prove the point. The problem I had was how to simulate this, you simply can't photograph stars in daylight on Earth. A little while ago I decided how to do it. Sadly, since then I haven't had a clear enough night to photograph stars (overcast skies are not a problem on the moon, they are in South East England). Tonight the sky was clear.
First of all the basic photography lesson. On a camera such as those used by the Apollo astronauts there are three things they need to worry about. The first is focus. This is irrelevant to this argument. The other two are shutter speed and aperture. Both of these alter the amount of light falling on the film (or in a modern digital camera the CCD). The wider the aperture the more light that is let in, the narrower the less. Shutter speed also determines the amount of light faling on the film, the slower the shutter speed the more light and vice versa.
For a photograph not to be under or over exposed these two settings must be correct. Here in lies a problem. You need more light to fall on the film for dim objects to show up. So if the Astronauts had chosen to photograph the stars, the lunar surface would have been totally washed out as a result of being grossly over exposed. As it was they went to photograph the moon. There cameras were set to the correct shutter speeds and apertures for the lunar surface. As a result the stars were so underexposed that they didn't register on the film.
Now to my practical demonstration of this. I decided to use a brightly lit window to simulate the lunar surface (it was my own window so I wasn't breaking any laws ). The camera was set up on a tripod and two pictures taken. I used a digital camera (a Canon PowerShot S50) but the priciple is exactly the same as a film camera. It was set on fully manual. The only thing that has changed between the two pictures is the shutter speed. I set the camera to black and white, because I live close to London and in a long exposure photo the night sky looks a ghastly orange.
In the first a shutter speed of 15 seconds was used:
In this photograph stars are clearly visible. However if you look at the lit window there is no visible detail on the curtain. It is over exposed and totally washed out.
In the second photo a shutter speed of 0.5 seconds was used:
In this photograph details of the curtain can be seen clearly. The window is now correctly exposed. However there are no stars in the sky.
Neither of these photographs have been touched up or reprocessed in any way, except to reduce them in size.
So there you have it, the reason why none of the Apollo pictures have stars in the lunar sky is just basic photography.
I hope this explains it.
"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001
...The greatest error is not to have tried and failed, but that in trying, we did not give it our best effort.
Posted 08 March 2007 - 01:53 AM
Waspie, of course, has it right.
...as does everyone else who has posted a response.
It's really rather simple:
The camera was set to photograph brilliantly lit objects in broad daylight...short exposure times, etc. The stars in the sky are no more visible to the camera than they are to the human eye in that realm...which is, not visible at all.
Photography assignments were geared toward recording the men, their experiments, equipment, and the lunar surface, and camera settings were made to capture those items, again, all lit by a broader daylight than is possible here on Earth, despite the black "sky".