I see on Facebook some conspiracy chatter regarding to how NASA falsifies their images. One of the points the conspiracy enthusiasts point out is the lack of stars in a lot of their imagery. I believe this all started with the Apollo mission pictures. They use the fact that you can’t see stars in the Apollo images on the moon as proof that they were never there. They believe it’s a gigantic hoax.
It is NOT a conspiracy just a physical detail on how film cameras and CCD’s function. It’s science not a conspiracy.
The critical factor for your eyes, and for pictures, is exposure. If you look at or take a picture of something that is relatively bright (which will include anything in the foreground of a picture from space), the exposure will be stopped down. Fainter objects will “disappear” from view. You will experience the same effect if you turn off an electric light at night: everything will go pitch black for a while until your eyes adjust and “open up” to begin to see some dim things illuminated by whatever ambient light there is. Similarly pictures from space that look only at stars, such as Hubble Space Telescope images, have the exposure opened enough and long enough to see lots and lots of stars and galaxies.
The issue is dynamic range. Any imaging system, whether a film camera, digital sensor, or event even the human eye, has a limit on the range of brightness it can process, from darkest to brightest. So imagine you rate all light sources on a scale from 1 to 10 and your imaging system has a dynamic range of 5. That means you can take a good image of dark objects if your exposure centers on 3 (and therefore covers 1-5), but in that case lights brighter than 5 will be overexposed. Or you could image bright sources by centering on 8 and get objects of brightness 6-10, though everything darker would be totally black.
Note that the human eye in many ways is a superior imaging system. We have a very large effective dynamic range since our pupils can expand or contract in real-time as we scan over a scene. Cameras, on the other hand, generally need to have a narrower dynamic range and the parameters of the camera (aperture and exposure) are fixed for a given shot. This requires compromise: You expose for the fainter light sources (and overexpose the brighter ones) or expose for the brighter part of the scene (and underexpose the darker parts). The same reason why it is difficult for a a camera to get a good portrait of a person back-lit by the sunset makes it hard to get a photograph of an astronaut in a space walk with a star-filled background.
The lack of any dim stars in any space imagery is NOT proof any chicanery. Just how cameras of all kinds work. When it comes to questioning anything scientific please defer to the people that understand it.
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